I recently went from an ATI Radeon 9500 Pro to a ATI AIW 9700 Pro and have noticed quite a big difference. On the 9500 Pro Unreal 2 was a bit choppy at 1280x1024 32 bit color and 2x AA/8x AF, but with my 9700 Pro I can play it as the same settings but with 4x AA and 16x AF and it's smooth as silk. I guess it just depends on your gaming needs, but I would say if you are a light gamer frab a 9500 Pro or 9600 PRo and overclock them, but if you're hardcore or just want the biggest baddest braqgging rights grab a 9700/9700 Pro. I would also interject that with newer games coming out the bigger better video card is going to definately allow you to keep your card longer, so for 55 bucks if you can keep your card a little longer, depending on your needs it might be worth it...
ATI Radeon 9500 Pro @ 351/313 - 3D Mark 2001 SE - 15002, 3D Mark 2003 - 4476
ATI AIW Radeon 9700 Pro @ 351/340 - 3D Mark 2001 SE - 17900, 3D Mark 2003 - 5300
Hope this gives you some ideas...