You should be able to pick up an 500/600W OCZ GameX/StealthXstream for around that price. I would also look around for an Antec Earthwatt or True Power Trio in your wattage range. Those are about the best you can do on that low of a budget. You may get lucky and find someone with a Corsair vx550 for around that price which would be a step up from the others. Another one to look out for would be the BFG LS-550.