The 7850's better than the 560 Ti at a similar price. A 650W PSU would be $40 cheaper, though, so you can make it to a 7870 Ghz at $240 after rebate: http://www.newegg.com/Product/Product.aspx?Item=N82E168...
If you're not really going to use all that hard drive space, get a ~$75 1tb drive and bump up to a 660 Ti.
Hey angryragtimer this build you have is great but i would change some stuff here. First off i would change the motherboard to an asrock z77 extreme4 it has really good features and etc. And last but not least for the case i would go for an coolermaster haf 912 great cable managment and great cooling for the 50-60 dollar budget range. For the Gpu crank your gtx 560ti to an 7870, but to get to the 7870 i would reduce the hitachi 2tb to an samsung spinpoint f3 1tb and the rest spend it on an 7870 they basically beat the gtx 660ti and it uses low-power consumption.
So basically from my point of view the build should be similiar to this: