Hey there donkeyjack, glad you got the replies towards building a new system. Anyways if your not into overclocking stick to the 3470, barely any difference and I personally would stay with Windows 7 opposed to Windows 8 which is a bit different from windows 7 and previous windows.
Anyways take a look at this:http://www.tomshardware.com/reviews/gaming-cpu-review-overclock,3106-5.html
As we can see the 3570k and 3470 is at the top of the list, generally Intel processors are better than AMD in terms of gaming.
However I believe in things like video rendering the FX-8350 kind of kills the i5. I hope your not going to do such things?