Thanks. Any recommendations on a gtx 460 card. Best bang for the buck? Or should I post that question separately somewhere else.
There are a few considerations of which you already addressed one of them, the PSU. The other considerations are how the case was designed for cooling and if the card fits with all the extra "stuff" that might be built in to the case. Other than that you should be able to use what ever you want. I'm using a Sapphire Radeon 5570 that was made for a smaller form factor but could also be used in a full height PCI-e slot, I'm getting 60 FPS in World of Warcraft with it and 40/50 FPS in 10/25 man raids. For the lower price, and seemingly lower end of the 5570s it does really well and didn't require a PCI-e power connector. Just look through the reviews of the "most ratings" and "highest ratings" cards, thats how you get the most bang for the buck.
Dell Optiplex 380: Intel Core Duo E7500, 8 gigs DDR3 PC3 10600 GSkill, Sapphire Radeon HD 5570 1GB 128 Bit DDR3, Windows 7 Professional 64bit, 500GB WD Caviar Blue HD, SIIG IC 5.1, Imation M-Class 64GB SSD, Behemoth Mouse, Logitech G-13, OCZ ModXStream-Pro 600W PSU.