Just a question... Do you need 300fps? Granted, I get ~180fps with everything at max, but then I game on a 120hz monitor as it is.
What monitor do you have? If you've just got a 60hz monitor then anything above that in any game is pretty much pointless.
Anyway, any of the latest i5s will be fine, but even AMD's 8320 will most likely be good enough. You'll get awesome frames still with something like a 760 (a single one gets me between 90-120fps), or an R9 270X.
Also, read this article for tips on improving performance in CS:GO, was published just today in fact!
http://www.pcgamer.com/2014/02/04/how-to-configure-counter-strike-go-for-the-maximum-competitive-advantage/
P.S. James Mason is an idiot (never thought I'd say that...), eyes don't see in typical FPS terms. Pro Quake players used to overclock their monitors all the way to and past 200fps, but that was in the days when that was more common and a bit easier.