I would actually think your video card is the bottleneck - it's 5 generations behind (I'm 7 behind). However, I'm running a 7600 GT with a very powerful i7-2600K just fine. The video card and processor combo doesn't matter as far as compatibility goes, but, chances are, if you upgrade your processor, you'll also have to upgrade your motherboard and RAM along with it.
However, your needs depend on what you do. If you're into gaming, then you'll want to focus more on the video card than the processor. If you're into video processing like I am, then upgrading your processor is more important. If you're only after Internet browsing, light gaming (like basic pinball or card games), word processing, or doing 2D graphics, then your system is more than enough as is.