LazyPandaReddit.com/r/buildapc
r/buildapc is bad. Just a bunch of intel fanboyism.
Right now the best value (basically) is a fx 6300, a 990fx mobo, 8gb 1866 or 1600 ram, and a 7870. But if you need to be intel nvidia than a 3570k and a 650 ti or possibly a 660 non ti, but that would cost more. Amd is the way to go unless you have tons of extra money•
Do you need to do all max settings? Or could you be fine just turning it down to medium or lower AA. Multi monitor? How much money are you going to spend.
Building it yourself is ALWAYS. ALWAYS the better option. Prebuilts cheap out on many of the most important parts, oem psus are usually complete shit. I'll link you to a pcpartpicker list once I get out of school (in free block right now)