Elaborate .... !? Sure, .... they seem to have drawn all the luck outta slush!. So, nothing here nor there!

And yes, keep them all pointed at slush and you'll reap what you deserve, I find the strategy of pointing them at different pools a "false economy" cum fools' gold of sorts.

Or you can get 3 of these for a fraction of the price:

http://www.ebay.co.uk/itm/3-Dustproof-120mm-Case-Fan-Dust-Filter-for-PC-Computer-/321604133471?pt=UK_Computing_Fan_Grills_Filters&hash=item4ae119a25f

The point about the fans being crap was in relation to the noise they emit AND the S5 being touted as a home miner.
On their own, the V34809 (if that is the fan used in the S5) with its Advanced Vane Axial Design, can hold its own and is well suited to a commercial environment and NOT a home one; and bitmain probably chose that particular design because of its efficiencies without taking into account the home mining environment as a major target market (but targeting them anyway!).

I am starting with the 550watt PSU because I have a good number in stock and have been using them for a good while, so I know their resillience and inherent value, but should there be substantial demand for the higher wattage ones, then I can see if I can source them in bulk to keep pricing reasonable.
Shipping world-wide can be an issue with server PSU's as postage can render the price un-competitive. Also, being 2nd hand, returns would be expensive / prohibitive, defeating the savings to be derived from server PSU's .

Bitmain listen, no doubt.
We asked for an EU presence to reduce shipping costs, and this is the opening shot on that. Leaves margin for the buyer ....  I like it.

try the bfgminer thread, someone there is bound to know what the heck is going on.
PS. Be sure to tell them what OS you are running it on too!

Just to recap, if the stock fan is the V34809, then with a top rpm of 5300 (and assuming a linear increase in CFM and dba), then to get to stock cooling levels you'd need:
(stock rpm / fan max rpm) * fan max CFM = Stock CFM
(3800/5300) * 220 = 157 CFM
Applying the same simplistic logic to the dba: (3800 / 5300) * 64.8 = 46.46 dba
Thus any fan that can provide over 157 CFM with a dba less than 40 would be better.

PS. I know I am most likely wrong, but please don't shoot!

That is a crap fan! It looks like the ones that ship with the AMT 1.2 miners (are they 12v 3A?) Do they have a sticker and care to post a photo?
The design of the safety /focus grill is what makes them whine (and therefore loud), but I suppose they were chosen because of the CFM they can output, but if running normally is 3800rpm .... then I wonder.

EDIT: I think this is the fan (220 CFM 12v 3.3A max 64.8 dba) - datasheet => http://www.nidecpg.com/fanpdfs/va450dcf.pdf
the ones that ship with the AMT 1.2 are V34809-INT1F

It is really a ping pong thing to call the 38mm as the standard ones ..... 51mm one may actually be the standard ones, but never mind, though you should have thought of the 51mm ones seeing I'd suggested they had 38mm blades ....

But more interesting from your point of view, is what CFM + noise level would you get from those 51mm fans, bearing in mind that the ones that come from the compaq servers are 12v 2.7A they are bound to have a higher CFM rating than those in the 51mm datasheet, i.e higher than 190CFM (of course even the dba), BUT at a reduced voltage, the dba will be less (possibly less than the stock /silverstone running at medium), and the CFM too (but possible higher than the stock /silverstone running at medium); then there you have a good substitute.

Yep they do, and more pertinent different depths.

38mm - 120CFM max 43.1dba @ 2750rpm => http://www.nidecpg.com/fanpdfs/c2003_4546.pdf

51mm - 190CFM max 56.7dba @ 4000rpm => http://www.nidecpg.com/fanpdfs/c2003_4747.pdf

I was referring to the latter type (model A34538-90 but can not find its datasheet though plenty on fleabay!). Also the CFM & noise levels at the reduced voltage should be the ones that matter, as I am sure they will be better than the stock fans, possibly even the silverstone.

Those are not ideas, they are the facts as I have them.
1. The NMB 4715KL has a 38mm frame BUT the fan blades / fins are, like I said, 25mm. I know this because I've just measured one. And it is classified as a 120mm fan.
2. The TA500DC has 50mm frame and the fan blades are 38mm, just like I said. It may indeed be classified as a 127mm fan (against my 125mm), but my point was that the holes on it will not fit a with the frame of an S1, and possibly S5.

I have no claims to make towards comparative noise levels, but like I suggested, I clipped mine with resistors to reduce the voltage / wattage and they work wonderfully with my OC's S1's with little noise, much better than the stock NMB 4715KL (even with the blue wire hack!). I put that down to the size of the fan blades.

And by the way, there is no speculation in my comment, and therefore no chance of confusing / mixing numbers like you did, just un-udulterated observation.

If you are going to try out another fan, I'd hasten to suggest you look for one with deeper fins. They will provide a higher CFM at lower voltage and be quieter. For example, the stock NMB 4715KL fans that bitmain deploy are 1 inch (2.5 cm) deep, whereas a Nidec TA500DC is 1.5 inches (3.8 cm). If you can get a 2 inch deep fin / blade on the fan, I think you'll get an even better airflow + quieter for if you run them at less voltage.

PS. The Nidec TA500DC is not a 120mm fan, more like a 125mm fan, and on the S1's that I run it on, the holes do not fit those on the frame, however, it fits inside the frame and I attach them using double sided tape, that and the pull layout make it stick rather well. Additionally, I run them without the PWM (though they certainly have PWM as they are 6 wire). You can pick these off flea-bay for a pittance, shipped.

Won't be surprised if it turns out those S5's you've deployed have a conflict of sorts with the pool .... they seem to have drawn all the luck outta slush!

Too damn right, if you clip a Nidec TA500DC with a resistor (to reduce voltage / amperage) you get a fantastic airflow / CFM with little noise. I think that is because the fins on the TA500DC are a bit longer (and more angled) than on the regular fans that bitmain deploy. I use a several of these on my S1's (don't laugh ... ) in pull position as replacement for the stock fans and they work wonders.

13hrs and counting ..... 12.75PH and rising .... the S5's have hit the network ..... and driving the pool hash-rate up ... they seem to have left the luck behind though!

Fair enough seeing the S1 has been, for a while now, know to have been EOL'd by bitmain, however, could you at least release / update the BM1380 datasheet to include the details that are available in the BM1382 datasheet, aka
1. The Typical hash rate and power table
2. The Work Input timing table

And if at all feasible without divulging your trade secrets, the functions available at chip level to set voltage, freq etc. This would enable intrested party further developement rather than having to depend on the goodwill of the cgminer crew. Believe it or not, there are still a number of S1's out there and despite bitmain having discontinued the line, we still use these machines.

I have neither empirical evidence nor electrical engineering know-how about what I am about to state below, but believe it to be true.

If you clock your S3+ to freq 250 with a voltage setting of 0750 then the total draw the chips would require would be approximately 294 watts. Now here comes the part I am not certain on, i.e I think you can achieve the stated hashrate of  504 Gh/s running it off a 400+ watt PSU, and that is where you would get the reduction in power draw at the wall (and not too dissimilar to the S5 9v PSU undervolt!).

I am also intrigued as to how the latest beta firmware reflects on the power draw when a voltage setting is applied as it seems to handle better than the previous releases, but again, not having a killawat meter bars me from gathering any data on that.

I do NOT have that problem, but it could be due to all those units using the same device driver file.
If you go to one of the units via control panel properties and find the path to the driver, then browse to the folder and create a few more folders under it (you can name them as you wish) and copy the driver into each folder. Then re-assign the drivers for your CP2102's to the different drivers in the new folders, ensuring each folder driver is assigne to only 4 devices (4 being your magic number!).

I am going to be offering some soon, but initially 550W Dell server PSU's each with cabling for 2 6pin PCI-e connectors.
1 should be good to power an OC'd S3 or an S1
2 will be required to power the S5 (use each to power a blade, do not cross power as per bitmain advisory)

I have not worked out a price yet as I am waiting for supplies' costings to come through. The cable braces will be available on their own (for far flung users that can source their own PSU's to reduce postage), but the price of the PSU will be dependent on the price of the batch I get, thus will be variable.

Like I said above, go to the S3 discussion thread and ask one of the support people, via PM and including your email, for the firmware and they'll send it to you via email. Dogie also posted a link to it here https://bitcointalk.org/index.php?topic=671189.msg9895096#msg9895096, though I'd get one from support direct.