Just a heads up for anyone deliberating between those 2 cards, who doesn't care about MSAA, and plays at a resolution under 1080p. I recently bought both of them, compared a few games with them, and found out the 650 ti is a beast for the price at 1050p and 720p with no AA.
I benchmarked a few games including Far Cry 3, Sleeping Dogs, Battlefield 3, Dirt3 and WRC3 and found there to be a less than 10% performance difference in almost all of them at 1050p without AA, apart from Battlefield.
720p is neck and neck. Around a 3% swing either way, with the 650ti being faster in Far Cry 3, Sleeping Dogs, and WRC3.
I also experienced a lot of microstutter with the 7850 playing Far Cry 3 at > 60fps, and none with the Nvidia card.
If you're playing at 1080p+ with MSAA, obviously the 7850 wins clearly, but if you don't care about MSAA and you're playing at less than 1080p - the 650ti is a great card.
In fact I think it's the perfect card for a gaming HTPC. Silent, low in power consumption, with excellent performance as long as you play to it's strengths.