AnandTech published a roundup of eleven cheap power supplies in the 350W to 450W range, you can check it out over here. The best unit from the comparison is the FSP Raider 80Plus Bronze 450W, but at $55 it's also the most expensive PSU in the roundup.
Some of you have suggested to review a few PSUs with 350W to 450W. Therefore we picked a collection of such units from well known and unknown manufacturers and tortured them with our overload tests. Read on to find out who delivers the best performance.
~400W is still plenty even for a midrange system, and with optimal efficiency generally coming at 50% load these power supplies should run closer to their "sweet spot" when idle as well as under load. There's still enough power on top to run a Core i7 or Phenom X6 processor and a discrete GPU.