CPU Affect on Mid Level Gaming

My questions is this. What is the affect of a significant CPU upgrade on mid-level gaming if the video card remains out of date.

For instance...

I have this system:
AMD Athlon™ 64 X2 4200+ 2.2ghz
2GB DDR 400 MHz (PC3200) memory
GeForce 7600GS

I am building this system:
AMD Phenom II X4 955BE 3.2ghz
4GD G.SKILL DDR3 1600 memory


I am keeping the GeForce 7600GS until the ATI 5xxx series is released. What kind of gaming performance increase will I see with the more powerful processor and ram, while keeping the same dated video card?

I do not play games like crysis anyway. I am an MMO player (WAR) and strategy gamer. The graphics for these games are never great anyway. I would argue that CPU processing speed is more important than graphics on some of my grand strategy games.