im using a 64mb Radeon 8500 at the moment and as long as you get the right drivers its fine.

But i saw in a magazine the other day that the ATI FireGL 8700 is retailing for around £200 but is optimized for 3d rather that gaming. so if you want a less expensive specialised card that might be a good choice. (althought i dont know how much better it is that a standard gaming card)