will a 4800x2 and 2gigs ddr2 800mhz ram bottleneck a 9600gt?

Those are my specs right now, and I am thinking about upgrading from a 7900gt to a 9600gt. Will they bottleneck? Is that upgrade a fair performance increase?

All depends on what resolution you wish to play first person shooter games. A bottle neck means performance is almost nothing regardless of what new hardware you buy. The point is at a very low resolution with the 4800 you could get near the same FPS. At 1024X768 and below It would give some bottle necks. At and above 1280X1024 you should see a good performance boost from the new GPU.

The games you play in the future will inch this CPU closer and closer to a bottle neck as more CPU performance is need for the none graphics parts of games. In the coming 2 years games may show little performance gain at 1280X1024 no matter if its the 9600GT or the 9800GTX. At that point your CPU would then be seen as a major bottle neck. Crysis at ultra high may be the only game that would come close to bottle neck this CPU.

If this system is for Elder Scrolls IV then all CPU's will be bottle necks as this type of game is CPU dependent.

It should still be a while before you see any real sort of bottleneck. Not to say that a 9600 wouldn't benefit from a faster CPU, but your CPU is still fast enough to see gains from going to it. You probably won't hit any real bottleneck until the next gen of cards (after the 9800 and so on).

For instance, I used to have an Athlon 64 3200. That would have probably been bottlenecked in the 8xxx series and going to a 9xxx series card probably wouldn't have produced much gain.