It is either gonna be the 5900 or the 9700 pro. They both perform extremly well in different areas. I'm sure that you will get crap like "ATI rapes the 5900" but that is just simply not true. They both have their strenghts and weaknesses.
You will end up paying almost $50 more for the ATI, when the differences are hardly noticable. And the best part aboug the link to the 5900 i posted is that it comes with a lifetime warranty (which i have had to use once on my ti4200, and they were great (BFG TECH)). And the 5900 easily overclocks to the 5950 on stock.
for the money this is a great card . i just put one in my father in laws pc i built for him and it is very nice . beats my sons 9600xt . read the reviews on newegg . they all say it is nice and it overclocks good . some say to 480/850 thats 5900 ultra speeds . and all for 188 $
Well to be serious... I would probably go with the 9700 Pro because I like video games and I'm looking forward to HL2. HL2 didn't run very well on the Nvidia cards, per Toms Hardware
"The ATI cards lead the pack. Most impressive is that the Radeon 9600 Pro beats the FX 5900 Ultra. The FX5600 needs to be run in DX 8.1 mode to get scores over 25 FPS."
If HL2 is anything like HL1 was, then it will probably be the new standard for video games. You want a card that will play well on the standard. If you aren't concerned with gaming then none of this really matters.