Okay, so I'm selling my iMac with an Nvidia 8800GS 512MB, and I'm wondering which card will be better to buy. Actually, I'm 99% sure the order of best to worst goes: 4850 > 8800GS > 4670, but my question is, how much more powerful is one over the other? Is the 4850 a ton better than the 8800GS, or just a bit? Is the 4670 a lot worse than the 8800GS? I'm mostly thinking about gaming here. Of course, ideally I'd get the 4850 but I don't have much money. Thanks.