Certainly the basics are OK. In order to overclock processor, you will need an aftermarket cooler, the stock one is not suitable, for overclocking. Would suggest CoolerMaster Hyper 212Evo.
There are a couple of things, I would recommend changing to better Quality/reliability:-
RAM: That RAM has poor latency (11). Ideally you want 9 (lower is better). Suggest Corsair CML, GSKill Ares, or Crucial Ballistic Sport.
PSU: Thermaltake not too good. Suggest XFX, Seasonic, Antec, PC Power&Cooling. 600w more than enough. (550w would be OK)
SSD: OCZ's Vertex 3 not their best. Vertex 4 is good. Alternatively Samsung 830, or Crucial M4.
GPU: The Gigabyte GTX 660 has much better performance (30%-80%), than the 560Ti, and same price. (plus lower power consumption- 550w would definitely be enough).
How would the gigabyte 660 (non-ti) compare to a gtx 570?
It's obviously a lot closer. The GTX 570 has very similar performance to 660, in some games, like Crysis, but still lags some way behind 660 in games like BF3 (by about 20%-30%). The GTX 570 draws a lot more power, though.
Btw I already ordered the ssd, only because I got it for $65 at tigerdirect!
How would a gtx 660 (non-ti) compare to the 7850?
When comparing GTX660 and HD7850, it does vary quite a lot, depending which games, you are looking at. Also the Radeon 7 series tend to overclock reasonably well. Taking everything into account, I would still say 660 has the edge, but only slightly, overall, maybe 5-10%. Within that, though HD7850 may actually be slightly better, at some games, like Crysis, Metro2033, Skyrim, Dirt3, but 660 would still have a decent lead, in games like, BF3, Borderlands, Starcraft, Portal.