evga 1600w is your best bet. 10 year warranty too. quality cables, quality power cable. all kinds of voltage protection. Its not silent - but there is a reason I refuse to get server psu's for my garage....the high pitch noise is too much. Sure If you have multiple s7 then getting atx will be expensive, but if you run one, invest in a 1600w, you can re-use it for literally anything after and its good quality.
Yeah that would be too spendy for me. I have 3 S7's currently, and another 3 coming in (batch

likely by Friday. Hence, 6 EVGA PSU's blow my budget out of the water.
I've seen the Delta 2000W PSU without the breakout board for $30 on ebay (and the breakout board is $45 I believe), so since I already have all of the PCIe cables I need, all I'd need is more C19/C20 cords, and some fans. I don't know how expensive fans are, but My guess is that I can probably get everything I need for around $100 each PSU.
OR, I can add those additional fans to the top like Jabber suggested. Jabber, when you have a moment, could you please send me those schematics and how they work? Thanks!