http://www.guru3d.com/article/geforce-gtx-560-ti-review/14
It's better than the 6870 that costs the same, and it's a lot better than the 460, but costs more.

An overclocked 460 at my speeds is > or = to a 470. The 560 is a bit faster than a 470 but you can overclock more.
In all honesty, if you SLI the 460's theres not really anything you can't play especially overclocked. I can ran any game maxed right now pretty much except like metro and stuff.
If you have the cash tho, yea the 560's in SLI is an amazing option. Only competitor is the 6950 crossfire
http://www.newegg.com/Product/Product.aspx?Item=N82E16814161355&cm_re=6950-_-14-161-355-_-Product
Currently seems like the best deal.
What do you use cuda for?
Only real thing it can be used for right now is folding.....
Those mirror things all over the walls are obnoxious. And the movement is laggy. Do not want.