bottlenecking depends a lot on the game you are playing.
on CPU intensive games like most RPG and RTS , the 2700k stock would be a bottleneck.
on most FPS, the GPU is the biggest bottleneck.
with BF3 as the current most GPU intensive game ever, the 2700k would NOT be a bottleneck with SLI gtx570.
I doubt that it would be a bottleneck even with tri SLI gtx570 !
i doubt that disabling HT will make a difference, but definitely do try that too.
AFAIK, BF3 does not increase performance with 4 cores over two cores at max settings. so a cpu bottleneck is unlikely.
one suggestion is to try disabling all AA and FXAA/MSAA from the options. those settings really hammer the FPS.
with AA, during intensive outdoor scenes, the fps takes a big hit.