Fx6300 vs i5-3570k in a gaming only build

I agree. If you bought a 7970/670 and then have money left over the i5 3570k is.a nice choice but like you said if you can't afford that you can get 6300 and a 7970/680 I personally bought a 7970 and a 6300 and the rest of my system (all together $1400) I still had about $300 left I could of easily gotten a i7/i5. However when you work hard for your money. And know that for gaming a overclocked 6300 is perfect I didn't wanna spend the extra $100 bucks for the i5. This is just me though. You sweat for the money you earn it's hard to give it haha  

Given those parameters and those options, I would have to choose the FX 6300 and the fast graphics card. As you can see (according to Tom's), the FX-6300 is only a tier below the i5 3570k when it comes to gaming. With only one tier separating the two CPUs, you won't notice the difference between processors gaming, but you will notice the difference with the faster card.
http://www.tomshardware.com/reviews/gaming-cpu-review-o...

I wasn't presenting these as the only options. I guess I was wondering if it makes sense to get the best gaming processor if you haven't got the best graphics card.

Well i mean if you already got The single best gpu. and you can afford a i5 its fine. However i would never EVER get a 7870+i5 3570k i would rather a 6300+7950

Here's something you may be interested in reading. Granted, it compares the i7 with the FX 8 core, but the premise should be the same.
http://www.tomshardware.com/reviews/fx-8350-core-i7-377...

optimizing the work load between the cpu and gpu is important. Lower rez taxes the cpu and higher ones tax the gpu, and in that recent tom's review we've all been reading lately, at 5760x1080 no cpu could push cfx 7970's.

which cpu you want to get depends a lot on the starting point of the gaming build which is the resolution you intend to play at.

at 1920x1080, 6300 or 3570K? is a more budget oriented question, go for whatever is cheaper. if its same price then simply flip a coin and you wont go wrong (not my line   )

and when its not the budget rather performance, then go for whichever cpu offers better IPC etc.

establish the context first. budget , performance, future proofing and OC headrooms for performance gain. Everything needs to be looked at carefully.

What if you already have a 7850? I can't decide between the fx6300 and 3570k. I will likely upgrade to a new video card in the next 1-2 years or put another 7850 in for crossfire...hmmm decisions decisions...

In your case, I wouldn't let the HD 7850 be my deciding point between the AMD or the Intel system. Final cost will be different between the two systems, all else being equal. (Myself, I'd probably go for the FX-6300 simply because I haven't built a Piledriver system yet. But I've put together several IB systems. But that's just me, because I'm more of a hobbyist than a gamer)