Q: my ATI X850 died and I found a Nvidia 8800GTS 640MB for $180. Is that a good deal and is 8800GTS better than X850?
A: eew. no. thats not a good deal at all. the 8800gts 640 mb uses the g80 chipset. for some reason nvidia used the g92 on later 8800gts's (the 512meg variety) making them much faster. since both of these cards came out, the radeon 4850 has appeared which is considerably more powerful. these are $170 and are much more powerful than the old gts you are considering http://www.newegg.com/Product/Product.aspx?Item=N82E16814125224 also, nvidia is currently a risky chipset to buy http://www.theinquirer.net/gb/inquirer/news/2008/08/12/nvidia-g92s-g94-reportedly note that this article applies to the g92 and not the g80 series. however the g80s are old and nowhere near as good as the g92's including the 8800gt. (I know its confusing the naming scheme went really awry with the 8800 series)