Personally, I think the 8-core is slightly overkill for gaming. Most games don't even use more than 4 at a time.

In my opinion, you should go with the 6-core 6350 (or 6300, if you're confident in overclocking). The money you saved on the CPU could then be put towards the newer, more powerful Radeon R9 280X GPU.

EDIT: I meant the 285.

And regarding your Power Supply: Make sure it's a good one! Don't cheap out on the PSU. It's very important to get a good, reliable PSU. Because a Power Supply failure can destroy the rest of your PC, or worse, can cause a fire.

Use this site, it tells you if there are any incompatible parts. i used it and it told me I had a incompatibility. All you have to do is add all the parts and on the top it will tell you if there is anything wrong with the pc build. There is usually a incompatibilty with the case.
http://pcpartpicker.com/parts/partlist/

Also click the rating tab so you can see which has the best ratings, if you want.

And for you too. I don't use TDP for my calculation. I use tests that measured the power consumption of the whole system at the socket. So when I'm saying the PC will in its whole draw 450 that is not conjecture but measured fact. Taking it at peak efficiciency the system will draw at most 410W directly from the PSU.

I'm not arguing for the sake of a few bucks but more out of principle. An Oversized PSU will always draw more power out of the socket than a perfectly fit smaller PSU. So 500 is good, 550 is still good. 600 will not plunge you into poverty but it's inefficient and so is everything above for this system.

I generally calculate only 80% power output (the minimum efficiency requirement for an 80+ psu), and substract from them max TDP GPU, max TDP CPU, 50W for Mainboard and RAM, disc and hard drives and other things possibly connected.

Some hardware with a tendency to consume more than their TDP sells give them additional extra Watts, in this case 30W for the FX CPU and 20W for the 280 GPU, for a total of 50W extra power need. I generally also leave a bit headspace in case the psu deteriorates.

Here, we got 140W CPU, 180W GPU, 50W Bonus for their consumption behavior, and 50W for Mainboard, drives and others, for a grand total of 420W; and 450W with the aforementioned headspace. 80% out of 600W are 480W, so just above my headspace. 550W psu will work too (440W with 80% efficiency rule), but I wouldn't go down to or even below 500W for this particular configuration.

@Vivster: do you use 80+ gold or even platinum psu? Because if not, you're riding dangerously close to the limit with your projected i7/Big Maxwell configuration. A 450W psu might suffice, but I wouldn't take a 400W, even though it will probably work just fine. The reason it does so though is that low power psu are generally just regraded psu with more power output, and most of the time this is due to market demands, not limitations on the hardware itself. But if you happen to fall on such a psu some day, expect a lot of bluescreens due to failing power supply.

Don't power failures due to low output usually result in black screens?

My current setup is a 3570k and an overclocked GTX680. I'm using a 480W Gold certified PSU from BeQuiet. I also use a fairly accurate measurement tool where my PSU is plugged in.

On performance tests and games my power consumption barely moves above 300W. That includes the efficiency rate of the PSU of course so the actual power that is drawn directly from the PSU is even lower.

Maxwell is extremely efficient compared to previous generations which results in a 980 that uses about as much as my 680 while being more powerful. I expect the big Maxwell will be around a 780ti concerning power consumption, which is for the full system about 350W including a current i7. Again, that's out of the socket, meaning the direct power draw from the PSU is lower.

So I have absolutely no worries going into my next system with a 400W PSU. If I can find one with enough cables for my system. Lower power PSU are usually pretty stingy with more cables. That's why I had to use a 480W for my current system.

Depends if a part gets no power at all or just not enough power, but you're right, black screens can happen, too.

I know the 980 is very efficient, moreso than your 680. On the other hand the 4770k conumes more than your 3570k, so it is a bit of a toss up. I would stay at your 480W psu if it's still in production or use a similar one, be quiet is a very good brand (using it myself, although a 5 year old 600W 80+ bronze model), and it's a gold model just like I expected from you.

Don't think I will take my old PSU. It would be the only part I'd keep from my old PC and I'd rather have a backup PC. I will probably not find a 400W PSU that satisfies my needs so I will probably go for 450 or 480 again anyway.

New stuff is nice. Looking really forward to it. If only Nvidia and Intel would hurry up with big Maxwell and Broadwell.

Honestly this is a solid setup.  I would reccomend the R9 290 at $270 is you can swing the extra cash, but otherwise you have got a solid build.

The 280X is no newer than the 280, and he sould NOT get that right now (280X is fairly overpriced).  However an FX-6300 + R9 290 wouldn't be a bad idea.

@OP: just a suggestion, 8GB can be fine for now, but it's the bare minimum, and if you see you're going to need more, don't make my mistake, upgrade the RAM before DDR3 goes out of production, or at latest little time after, because when it will go out of production its price will stopp dropping, and after a while it will rise again.