So I have an FX 4100, currently overclocked to 4.4ghz, and a Radeon 6950 2GB. I was considering getting a GTX 670, or an i5 2500k and upgrading the GPU later. I game at 1920x1080, and would like to run at highest settings or close to.
So, i5 or GTX 670?
My other specs include 8GB of ram and a Corsair 600w PSU.
More aboutshould upgrade
go for i5, your video card is pretty good.
do you have an actual problem you are trying to solve? unless you are at extreme resolution you may not see much difference.
I´d get the GTX 670 -- it will be a bit faster than the actual HD 6950 2GB, but the main difference you will notice is the AF -- anisotropic filtering, which will be almost the double texel rate. There should be also an improvement in pixel rate.
I have a 6950 and a phenom II 955 - my plan (depending on how prices go) is to upgrade the cpu first then maybe stick in another 6950 a little bit down the line...
Like the OP says if there's a specific problem find the cause first and then upgrade according to that...