Are you trying to upgrade a laptop? (if you are, most likely you can't upgrade the CPU since they're usually soldered onto the board now... and GPU upgrades are literally impossible and not cost efficient)
No, I'm buying a new laptop. It's the lenovo y510 with 15 4200m and dual GT 750s
I'd recommend getting some kind of a i7 with a better single card GPU set-up...
But no. the i5 should not bottleneck the GT 750s in SLI.
BF4 and Crysis 3 will run like maybe high settings at 720p with those specs.