you should have enough bandwidth not to bottleneck the card theres less than 25% differnce between the core 2 quad and the i7 920 i get about 55 fps on high settings. but i like aa on, you should get pretty close to that because bf3 isnt cpu bound.
i notice a lot of people saying get an i3 because you can play bf3 well on it. but you can play well on it on an athon x2 which is substantialy weaker than the i3... the thing they forget is that bf3 was developed for pc on pc... its not been developed for consoles and then ported back to pc... if they had of done this then the i3 would be under spec by a full core. to get the best from a range of games your best getting a quad just so you can max out 2 cpus and still have enough cpus spare to run things like the havok engine that handles physics and compensate for any bad coding.
just look at gta 4 if you dont get what im on about.
http://h11.abload.de/img/cpu_02qjb7.png you can see from these benches that the game isnt relient on cpu power... as they use a 580 and thers still enough grunt in the athon not to cause a huge bottleneck
but run a 580 on a game like starcraft 2 or witcher and you will see the athlon crumple under the strain.
where i think the problem lies is a lot of people look at benches but dont play a lot of games... so often dont understand the benches at anything other than a basic like for like comparison...