Like matto said the 660Ti should be close in performance to the 670 according to the current leaked specs. However if you can get a GTX 670 for 399 plus shipping on newegg its probably gonna beat the 660Ti in the long run.
The 670 has impressive overclocking capabilities and you wont regret it. And 40 dollars is a small premium for the 256 bit memory interface, that interface will help with performance at 1080p and higher resolutions.(such as WQHD 2560×1440)
Otherwise you can always wait for the reviews and compare the benchmarks to see, though I'm betting the 670 is going to win by far. They will probably lower the clocks on the 660Ti reference for release, though overclocking them to compete with the 670 shouldn't be difficult at all.
Yeah thanks guys for the quick response I was thinking about the FTW which is a FTW for me!