If Starcraft is your only game, a GTX670 is already a lot more power than you need. Don't bother with SLI yet - you can add another card when you need.
Ooof, he's got a super tough choice now.

Starcraft 2 performance is hurt by hyper-threading. LOLOL.
The i5 iterations get higher fps, The difference is subtle, but there.
If one's are actually serious about SC2, definitly get 2500k or 3570k,
HOWEVER, he's also using photo-shop, which benefit from i7,
If one's serious about photo-shop, go with 2600k or 3770k
As for the difference between z68 and z77, THERE is no worthwhile difference. Both platforms will support pcie3.0 with an ivy-bridge CPU.
NO other feature differences between the two are worthwhile.
Decision 1 is, i5 or i7
Decision 2 is, Ivy or Sandy
Decision 3 is, Z68 or Z77
I really wouldn't go x79 at this point, unless you have serious cpu workloads, like if you're a scene encoder. :ninja:
^_^