Some stuff to look at:
http://www.tomshardware.com/reviews/geforce-gtx-650-ti-boost-gk106-benchmark,3463-11.html
With the Radeon HD 7770 at $120, Radeon HD 7790 at $150, and Radeon HD 7850 above $180, Nvidia is rendering all three products ineffectual at their respective price points. With one swift stroke, the company engineered a hostile takeover of the $100-$200 market, increasing graphics performance at any given budget in that space.
More stuff:
http://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_650_Ti_Boost_SLI/22.html
As you can see on a performance per dollar basis, the 650 Ti boost "rules the roost" .... but what ya may not have noticed is that for a whole lot less money, in SLI ($280) they outperform the single hi end cards which cost much more:
7970 Ghz Edition has 98% of the performance of twin 650 Ti Boosts but costs $410-ish
Stock 680 has 93% of performance of twin 650 Ti Boosts but costs $410-ish
That's 46% more money for less performance .... and as the article says ..... no multi card problems observed.
2GB MSI factory OC'd model with $75 game coupon = $140 each
http://www.newegg.com/Product/Product.aspx?Item=N82E16814127728
As for the Ghz version of the 7870, it comes out 3% better than a 650 Ti in performance per dollar .....
http://www.techpowerup.com/reviews/VTX3D/Radeon_HD_7870_XT_Black/30.html
as we saw here ....
http://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_650_Ti_Boost_SLI/22.html
The 650 Ti Boost comes in 13% better than the 650 Ti which puts the 650 Ti Boost more than 10% above the 7870 Ghz on performance per dollar basis