one of my buddies was telling me about his 5 ants. by undervolting/underclocking, his electric bill goes down $120/month, and his mining revenue only goes down $30-40/month. not a bad trade off. plus they are cooler and quieter.
These are the ones I use, rated for 900w on 115vac, 1,200w on 220vac http://www.amazon.com/1200W-HP-DL580G5-Supply-440785-001/dp/B002P5XUA0/ref=pd_sim_sbs_pc_4?ie=UTF8&refRID=0RR4R5ZBJ24X4E6JSP8N You will use less power as well as they are >96% efficient vs 80-86% for regular PSU.
How to wire them http://www.rcgroups.com/forums/showthread.php?t=2100680
Instead of using a resistor between pin-1 and pin-4 I wired a lil' switch to them for easy turn-on/off. Close the connections and the outputs turn on.
To feed 2 OC's Ants I run two 12ga wire pairs from the PSU and terminate each pair with 2 (4 total) 12" PCIe extender cables from Frozen CPU. Cut the socket ends off of course. Think the cables were around $8 each.