The differences between 660 and 660ti are minimal at your resolution of 1440x900
The 660ti you linked has a slightly higher boost clock, but its probably a difference of a couple fps.
The 660ti "may" have a better PCB and may support "some" user overclocking; the 660's may not be great clockers either but in terms of component quality; the 660ti is better.
Unless you were doing multi monitor setup; i say opt for the 660. It will be enough to play Battlefield 3 at High Settings; and possibly Ultra Preset at around 55-58fps. It could be lower, multiplayer can be spontaneous so expect some drops if youre playing at Ultra with a single 660. MSAA can be pretty heavy so you can turn it down to 2x MSAA to get better frames.
If you were planning on resolutions higher than 1080p or doing multi monitor id say opt for a 670 or a 760. If not, a 660 will do perfectly fine; no reason to spend the extra for the 660ti (if you plan on keeping it stock)
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