do i need a psu? what do i use to control it?
You need:
a PSU of at least 600w bronze per s3. (i'm using a 100w gold PSU for my 2)
and a web browser to go to the ip of the miners for configuration purposes (default 192.168.1.99)
My 500W Corsairs are working just fine. I don't intend to oc, so it's OK that the 500W only s 2 pci-e.
I'm not surprised at all. The Corsair CX500 (if that's what you're referring to) has a maximum of 456WDC on the +12V rail which equates to 536WAC at the wall at 85% efficiency. At 80% load (20% headroom), the CX500 would be drawing 429WAC at the wall. Therefore, buying a CX600 or a CX750 to power a single S3 is a waste of $.
Current CX500 deals at the Egg:
CX500 - $29.99 after $20 rebate
CX500M - $34.99 after $20 rebate and $5 off promo code