the ivy chips are better for the average user.. The sandy chips are better tor those on a bit of a budget but like to push it oc's and the SB-E chips are for the people that have either more money than sense or really will use them..
Same goes for i5 v i7... i5 for general usage i7 if you'll actually use the extra threads (rendering number crunching etc)
Personally if I was building a gaming / media / web pc now I'd get the Ivy equivalent of the 2500k (3570k)
ps don't worry about pci-e 3.0.. as show in the 690 review, 3.0 to x16 2.0(or 2.1 can't remember) is basically no difference and so even a z68 board is an option if the z77 boards are too pricey
To be honest.. you could save a boat-load and have a very good gaming rig with a quad core phenom II 980
Cpu has very little effect on games once you get to a certain point.. for eg:
Intel i7-3770K Ivy Bridge CPU Review
and most of the games it has an effect on you have such high frame-rate that it makes not difference anyway..
Not that I'm saying to go amd.. But there is very little wrong with an amd base for a gaming pc and you'll see very little if any difference between the bigger Intels.