I went with the Ant Miner S3+. So far I am learning a lot and happy with it. I wish it was a little quieter, but that's not a big deal. The price was right too.
okay here is a safe easy mod add the silverstone 141 fan to the side that does not have the externet jack.
look at this screen shot I will post it in 1 min
see the silverstone spins at 1000 vs 2000
if you set at freq 200 and never change it is possible
it will be quiet .
as to your question can you switch from 100 to 225 yeah but don't
go under freq 150 . it will be good enoguh and with the silverstone 141 at amazon it will be quiet
http://www.amazon.com/Silverstone-Cooler-Computer-Cooling-FHP-141/dp/B00A460TK6/ref=sr_1_1?ie=UTF8&qid=1444248293&sr=8-1&keywords=silverstone+14116.99 amazon prime
look at my fan speeds below
I will check that fan out. I have found that any fan speed below 1900 RPM is quiet enough for me. What version of the firmware are you using? My screen looks different, your fan information is below the frequency information, while mine is in-line with it:
