Here's a thought if the op were buying now. Maybe instead of the 660ti look instead at a GTX 570. http://www.newegg.com/Product/Product.aspx?Item=N82E16814127682
They are about 50 dollars less, but surely performance can't be that far off. Perhaps take the money saved, pick up a nice SSD. I recently got a 64gb ssd for my older rig.
Myself, still soldiering on with my Athlon II quad core, AM2 board, 6gb of ddr2 and GTS 450(rig does everything I need, what can I say? Next upgrade probably a better PSU and video card though).
But, I have a 1 tb mechanical drive that I use for storage now. I added the 64gb that I picked up for 50 bucks at Microcenter, and now Windows 7 is a 7.0 overall. I think I'm rated at 7.3 on my processor and 7.2 on ram and graphics. My SSD is supposed to be SATA 2, so I think my older board is holding me back. But even then, performance is great. Applications are snappy to launch, there is literally almost no welcome screen as I wait for Windows 7 to boot. The biggest delays in boot time for me are waiting for my PC to post and getting to the Starting Windows splash screen.