700W is very nice.
Good ATI cards have already been suggested. I'm more of a Nvidia guy, so I'd chip in the GTS 250, which is around what you want to spend (a few bucks above it), and it is comparable in performance to the HD 4850 and 5750. The older 9800 GTX and GTX+ are solid choices as well and cost about the same. All of these cards, including the ATI ones cost about the same. Might be worthwhile to hunt for discount offers or otherwise good deals.
Plenty of different vendors to choose from. I tend to go with Gainward, but that is more tradition than anything else

. I often stick to brands and manufacturers whose products don't give me trouble. Other examples are NEC for monitors, Hitachi for drives, Razer for mice, Logitech for keyboards, Intel for CPUs ...