considering your psu restraints, i would go with nvidia. plus their cards tend to be smaller and produce less heat anyway. see if there psu has a pci-e 6 pin connector. if so, you can get a 7900gs for pretty close to $90; i got an msi one that supports hdcp off of ebay recently for $95 shipped. if you don't mind paying more you could go with a 7900gt or 7950gt, afaik those are the highest end single slot cards that nvidia makes (would consider ati, but your psu limitations...). if you don't have a pci-e connector on that psu and you don't want to replace it, consider the 7600gt.