anyone who says that this card performs very close to the 670, i don't know where you're getting your numbers from. MAYBE if you overclocked the hell out of the 660ti you would get the same numbers as a stock 670. Look at this review: http://www.tomshardware.com/reviews/geforce-gtx-660-ti-benchmark-review,3279.html
The 670 usually performs by 7-15 FPS better at 1080P than the 660ti. While the 660 comes within a few FPS once in a while, it doesn't do so consistently. That being said, I would imagine you want the higher end card since you're doing more demanding gaming with that 3D vision stuff. I haven't seen any numbers for it but logic would tell you that the 670 performs better than the 660ti; it IS a high-end card while the 660ti is a mid-range GPU. To me the extra $100 dollars are worth it and those worries about the cut-in-half memory bandwith are right.
I've had a gigabyte 670 windforce OC for over a month and it plays BF3, Skyrim and The Witcher 2 on either the highest or mostly highest settings at 60FPS (i keep adaptive vsync on for most games). I imagine your numbers with 3D wouldn't be as high, but would still be higher than the 660ti. If you overclock the 670 a little bit, it performs like a 680 because the difference between the 670 and 680 is smaller than the difference between the 660ti and 670.
if you are absolutely strapped for cash, the 660ti is fine but if you can spare the extra 100 $$ go for the gigabyte windforce 670; it comes factory overclocked but you can overclock it further as it cools well.Edited by ParadoxEternal - 8/18/12 at 11:19pm