I don't even...
You're right, you may want to consider a 3.4-3.6GHz+ i3, those are exceptional CPUs, from what I've seen the hyperthreading almost makes up for the lack of cores.
I think pretty much the same principles apply with the Phenom IIs and FX chips, if you're playing games which utilize the 4-6 cores the Phenom II X6 will likely take the lead, CS:GO from what I recall benefits from single-threaded performance, I haven't tested it as of yet so I can't really say, but I've heard from many that the G3258 performs really well when clocked up.
I'll test it if I can remember when I get my GTX970.
Check the OP in this thread, I go into where the G3258 wins and loses.
A short explanation, multi-thread dependant or heavily multi-threaded games the the Quad, Hexa and Octo AMDs will win.
Single-thread dependent, the G3258 will win.
Assassin's Creed IV: Black Flag may be the finest example I have to date.