The i7 920 is still a great CPU. Instead of replacing it, I'd recommend getting an aftermarket cooler and overclocking it into the 3.n GHz range. Some people can hit 4.0-4.2, but somewhere around 3.0 you should unbottleneck any GPU config you would need for BF3.
You could SLI your 460 (that's what I'm running), but if you have that much money to work with and with new generations of cards just around the corner, I'd sit on the 460 for a bit and then upgrade. This, of course, depends on the resolution you're running. If you're at 1080p or above, then what I said above holds. Below that res, 2x Hawk might be just what the doctor ordered.
I would start off with an SSD maybe the Intel® SSD 510 120GB or the Intel SSD 320 80GB as a boot drive and then the second video card. I would be careful about spending too much money on the Intel Core i7 processors since they are fading away and the 2nd generation Intel Core processors are outperforming them. Maybe look into overclocking Intel Core i7-920 to get you a little more time.
Since aftermarket cooling is pretty cheap i can go ahead and grab a fan for my i7. Ive never overclocked before but i bet i could find a good guide somewhere.
I am not familiar with Raid 0 or RAID setups in general but i also bet i could find a guide somewhere (unless someone has a link!) I will probably get 1-2 SDD. Mainly i will only be playing BF3, skyrim and sc2 or something similar but mainly bf3!
Since the 460's are pretty cheap i might go ahead and get another 460 to SLI. I have a rocketfish case and it's almost as big as i am so i have plenty of room although i dont know if the case cooling is as good as i want it.