Kinda coming in late, but my opinion would be a mobo and proc upgrade. It's obvious that you don't have unlimited cash to burn, so I would stick w/ the 8800 for now. The other guy was right that 250's are basically the same card and not worth putting dollars into upgrading. If you're Vista is running fine I wouldn't put money into W7 either. Not a cost effective upgrade in terms of gaming performance. My hard drive died so I'm upgrading to W7, but honestly it wasn't too high on my list as my system has been running great w/ Vista on it. I donno what your interest in hard drives is, but you might want to at least check out the new SSD's on the market, they are SEXY and going down in price...kinda.

Just my two cents.

Good luck w/ the upgrade and happy gaming!