Have you thought of swapping out the 660 ti for a Radeon 7950 3GB, I have used both of these cards before and prefer the 7950, with a mild overclock this card can be amazing, I believe it is worth the little bit of extra money if you can afford it. I have also experienced bad luck with MSI but according to my friends thats just me.
Ya i would rather a 7870 or 7950 over the 660ti. The 660ti has a 192 bit memory bus which might end up limiting you at high levels of AA and other settings. And Nvidia is just overpriced compared to AMD IMO.