Do you know the graphics card overheat or do you assume so because it crashes?
If it was a replacement shouldn't they be able to replace it with yet another one which worked better?
Do you have any case fans?
Your A4 6300 is quad-core but it's a weak processor.
Here's a comparison of the processors available for the motherboard you already have:
=2083&cmp[]=1997&cmp[]=1935]http://www.cpubenchmark.net/compare.php?cmp[]=2083&cmp[]=1997&cmp[]=1935
The Athlon X4 760K has four cores instead of two, the A10 6800K is also somewhat higher clocked and still have the integrated graphics. For the price though and a cheap upgrade I guess the X4 760K could be a decent choice?
It's still not as good as the i3 4170 which is a dual-core chip from Intel with hyper-threading. But that chip cost 50% more and you also need a new motherboard for it (socket 1150) so total price would be more than twice as much:
=1997&cmp[]=2522]http://www.cpubenchmark.net/compare.php?cmp[]=1997&cmp[]=2522
For more of an upgrade but also at a higher price would be the quad-core chip from Intel called i5 4460:
=1997&cmp[]=2522&cmp[]=2230]http://www.cpubenchmark.net/compare.php?cmp[]=1997&cmp[]=2522&cmp[]=2230
It's more powerful than anything you can put on your motherboard but the price of the upgrade would be 3+ times more than the Athlon processor.
And here's a test of three Intel processors:
i3 4170 - 3.7 GHz, 2 real cores * 2 threads / core
i5 4450 - 3.2 GHz, 4 real cores
i7 4790K - 4.0 GHz, 4 real cores * 2 threads / core:
=2522&cmp[]=2230&cmp[]=2275]http://www.cpubenchmark.net/compare.php?cmp[]=2522&cmp[]=2230&cmp[]=2275
Where the i7 4790K is the best you can put on a socket 1150 motherboard. It's also over-clockable.
Maybe compare your chip vs upgraded Athlon processor vs i5 4460?
=2230&cmp[]=1997&cmp[]=2083]http://www.cpubenchmark.net/compare.php?cmp[]=2230&cmp[]=1997&cmp[]=2083
Passmark may not be the best test for gaming performance but
In general the AMD processors perform poorly in games relative number of cores and clock.
The top of the line eight core processors most often doesn't catch up to the top of the line four core processors from Intel in DX11 gaming/titles.
So for a cheap price which seem to be what you've been going for the 760K I guess would help somewhat.
For a good gaming CPU you'd have have to exchange both motherboard and processor and spend more money which I don't know whatever you'd want. For simplicity I'd suggest something like the i5 4460, the Xeon E3 1231-v3 or the i7 4790K in whatever price category then.
800 watt PSU is plenty powerful. Now you had a AMD graphics card but it's still kinda over-kill, but at least you're safe with that one whatever you take even if the most massive most demanding AMD choices.
Idiot URLs and idiot page. Tried them with three different ways of posting the URLs. Too lazy to short them down to something which actually link cleanly. You copy-paste them instead.