Need help - building my first "mini" rig

[johnnydoe]

Hi,

I plan to build my first "mini" rig.
The plan is to run on linux, via usb stick

The hardware I plan to buy:
(Based on "cheapest" I can in the store except for GPU and PSU)
=====================
1) GPU = 2x "Sapphire 7950 3GB GDDR5 HDMI RETAIL DUALX with Boost"
2) CPU = 1x Intel Celeron Dual-Core G1610 2.6Ghz
3) MB = 1x "Intel® H61 Chipset" Gigabyte\MSI - (store: "Whats in stock"), from what I saw the Gigabyte have "1 x PCI Express x16 slot, running at x16" and "2 x PCI Express x1 slots"
4) MEMORY = none
5) HDD = none
6) PSU = Seasonic watts

Questions
=======
1. Any general comments\advice, anything I need to check/look for ?
2. I'm confused about the PSU, I saw the GPU draws about 225 watts each, but in AMD's website they recommend 500 watts and even 750 watts PSU for 1 GPU.
"How many watts" should I get for 2 GPUs ?

Thanks a lot for your help !,
J.

[Wassupia]

advice: calculate how much your monthly profit will be. don't forget to subtracks the electricity costs (in my opinion: even if you live with your parents, as they paying the electricity bill for your mining operation kinda equals taking it from their wallet) and the rise of mining difficulty for the next months.

personally, I fail to do a calculation that indicates investing in GPU mining would still be profitable (enough?) to make the investment (time, effort and money), but maybe that's just me not taking risks or being wrong.

about the power consumption:
http://forums.anandtech.com/showthread.php?t=2341040

if you want 2x 7950 mining scrypt, and possible overclocking, you'll need a big power supply, or may two. If system uses eg 600 watts on full load (probably more), you should take at least 750W or so, because your psu should never be running close to 100% of its capacity. If it's running 24/7, you definately need way more Watts than that.

[Treggar]

I was running 2 stock voltage R9 290's off a 750W PSU and the R9 draw alot more power than 7950.   NP.

[johnnydoe]

Thanks for your help, and I have one more question  in the end

@Wassupia
The monthly profit has many factors which cannot be measured, but I'm willing to take the risk also because of ideological reasons. 

@Treggar, @Wassupia
I think I found this PSU in reasonable price - "Seasonic M12II-750 Bronze 750W" which I hope will do the work

Regarding hardware:
I have a question regarding the m/b I planned to buy:

I will start with end - my question is:
Can I connect the 7950 to a m/b with PCIe x1, and still get the highest hashrate of this GPU?

Explanation:
I've checked with the store, and the available m/b is this one:
ASUS H61M-K
https://www.asus.com/Motherboards/H61MK/#specifications

It says it has the following slots:
1 x PCIe 3.0/2.0 x16 *1
2 x PCIe 2.0 x1

And I planned to use it with the following CPU - "Celeron G470"  (bcz its the cheapest this store sells)
From here it says that Celeron will not utilize PCIe 3.0 -
http://forums.anandtech.com/showthread.php?t=2316826

And anyway I planned to put 2 GPUs, so I need to use one x1 slot.

So back to the question -
Is this will decrease the mining hashrate ?
Should I look for a m/b with 2 slots of x16 ?

Thanks for your help !,
J.

[Treggar]

Using x1 slots doesn't effect your hashrate.  Just get a pci-e x1-x16 riser cable.  You can even get 2 and plug one of them into the x16 slot.   That's what I do ... my board has 3 x16 slots and 1 x1 slot, I just have all 4 of them running from x1-x16 risers.