Well I've played BF3 on a GTX 260 and 275 at 720p, both of which seem to have no problem at that resolution. Both are on quad cores over 3ghz with 8gb of ram. The only thing that could be a limiting factor on your GPU if it was a 512mb version, but I don't think the x50 series has had a 512mb version since the 250 gts.
Take a look here and see where these cards stacked up on the review.
NVIDIA GeForce GTX 550 Ti Roundup: ASUS, EVGA, Gigabyte & MSI
1680x1050 is a much bigger pixel count than your 1368x768, so you should easily be able to get way more than 60fps on high with no AA and HBAO off.