I know the primary difference or rather, the only difference between the two is that 660 ti has a 192-bit memory interface and the 670 has as 256-bit memory interface. My question is what can a 256-bit system do that a 192-bit cannot?an example would be nice.
+1 to Sumukh. Don't worry about bus widths, just look at results (benchmarks). GTX670 averages 15-20% gain over the GTX660 Ti. Bit less in some situations and a bit more in others. Up to you how much money you think that gain is worth, though I'd personally spend the extra.