Newegg.com has the Cooler Master eXtreme Power Plus RS500-PCARD3-US 500W ATX12V v2.3 Power Supply for a good price.

1. Newegg Combo Price : $64.98 Shipped
2. Rebate1 Price : -$10.00
3. Rebate2 Price : -$10.00
Final Price : $44.98 Shipped After Rebate