Hi Mineman,
As you can see from my system in my sig, i have the same Cpu as you but also a Gigabyte 7970 Ghz edition and my thoughts are;
The cpu isn't "that bad" maybe not as bad a people think anyway, it's done the job for me in all the games i've thrown at it so far, but.....
It's not great, and while it's worked for me, please bare in mind that it's with the CPU overclocked to high heaven (4.6 for the most part and now 4.9-5.0ghz depending on game) so the card could breathe as much as possible and not get bottlenecked.
You will need to overclock the cpu to get the best Fps possible.
My advice to you would be to get an FX8350 and a 7950 if you have £400 to spend, you'll noticed a huge difference in fps and depending on your Res, you should have no problem maxing out any games.
I'd also like to add that a few days ago i had the chance to pop a FX8350 in my rig, and even at stock clocks, my scores in both 3dmark firestrike and heaven valley benchmarks increased by a fair bit, Showing i believe that even at 5Ghz, the fx4100 was still bottlenecking my card.