One of the hardware review sites that I check out regularly (HardOCP, Anandtech etc I don't remember which one) mentioned that Doom 3 is going to use 80mb of textures. If that is really the case then you will definately be served better with that 128meg Radeon 8500 over te 64meg unit. If you know you're going to upgrade your vid card before Doom 3 comes out then maybe you save yourself $30 and go with the 64 meg version. I will be honest though and this is a bit off topic. I'm still a bit disapointed in the little problems that pop up with the ATI cards and their drivers. GTA3 and Die Hard Nakatomi plaza come to mind. I don't care how piss poor the programming is on those cards, the problems aren't there on my Geforce3. Now, if I had to buy a vid card today. It would be the Radeon.
Hope that helps a bit.
- J