I paid $690 total for 3x Antminer S3 and 2x EVGA 650W Gold psu's. Seller sent them via next day Fedex.
Just curious on what you paid?
Well how are you going to overclock 3 S3's with 2 power supplies that can't supply enough current to do it??
Each S3 at 250 will draw 400+ watts.
I would connect just 1 or 2 and try to overclock them 243 and 250. if they work then it is what I noted, the power supplies cant supply the amps needed for 3 overclocked
400w at 500gh is pretty much the ceiling for OC. The combined power of 2x650w supplies should be sufficient if there's at least 600w(50a) on the 12v rail for each.