I got an "Sapphire Radeon X600PRO 128MB DDR" myself,
and it runs Counter-Strike with no problems and 99,8-99,9 fps.
I didn't find a price of the X600 but I found an X800 at ebay, no
auction, buy now only.
The price is: $31 + $5.90 shipping
And here is the link: http://alturl.com/ota7