Why are you running a 32-bit version of Win7 on this system?
What sort of "bottleneck" are you expecting? The GTX 670 should provide significantly improved performance for your graphics. If your PCIx bus cannot handle the full bandwidth of that card, then you may not experience the full performance of the card, but it should still be better than the GeForce GTS 250 you are using now.
A new CPU won't give you better performance unless you upgrade to and i7 with more cores, and at LEAST the same core speed (3.2GHz).
So, get the new video card, change to a 64-bit OS, and add RAM.
I always had 64-bit, but after some guy fixed my PC he installed 32-bit for some reason. Do you need to format to upgrade it or can it just upgrade th system like I did from Vista to 7?
The PCIe bus isn't really the problem. The card is PCIe 3.0 while mine is 2.0, but the two are compatible and I've read that the card doesn't fully saturate the bandwidth of even 2.0, so I'm fine there. The real problem is, I've read that if you have a bad CPU, it can cause the graphics card to not reach it's full potential, thus the bottleneck. I don't know if this is really the case that's why I asked here.
I might upgrade to 64-bit when I have another drive to backup my files to, and I'll get myself some new RAM DIMMs when I buy the card. I just want to know if the GTX 670 can't reach it's full potential in my system, what other card can reach the potential that the GTX 670 will in my system?