Corsair CX500 PSU
Has a $10 off instant rebate, and also a $20 mail in rebate.
Brings the price down to $29 with all the rebates, you can't beat Corsair quality at that price
^I was considering the same PSU. Are you sure this PSU will support the XFX Radeon HD 7870 2GB?
xfx pro 550w core edition or the Sea Sonic S12II-620 Bronze. If you go for corsair get the cx600, but I highly recommend the first two.
^I like those but they are way out of the budget