No one can, of course, say how demanding BF3 will be.
But as some of the others are suggesting, I would also recommend holding off until the next GPU series are being released. It will presumably make the current line of GPU's fall noticable.
I respect your non-Nvidia thing, but honestly, a GTX 460 or GTX 560 is not bad.
However, The HD 6850's in Crossfire
should do you very well. It performs the same as my GTX 460's and I am able to play anything besides Metro 2033 on highest graphics (while Metro being terribly close) with decent FPS. I really doubt BF3 will overtake Metro 2033's throne. By all means.
When the Radeon HD 6850's in Crossfire are overclocked, they may perform on level with the GTX 580 in quite a few games.
If we assume you pick up 2x HD 6850, you will not need anymore than 550W at most.
Like the Antec EarthWatts EA650
and the Corsair TX650W V2 PSU
. They are both very decent and durable (with the Corsair being modular), so I would recommend those for your needs. They're not that expensive.
However, for Crossfire/SLi, four 6-pin connectors would be preferred, though they are no must. These only have two each.
At 1080p, 1GB will be enough. My GTX 460's only struggle with Metro 2033 because they lack memory, while they are actually fast enough to play the game at max settings. And Metro 2033 is the only game I have had the memory issue (damn you, MSAA).
A PII x3 will presumably bottleneck your GPU's if you choose the 6850's (that setup is just an example to give you a slight heading about memory, speed and bottleneck). Perhaps about 10-30%.
A PII x4 will do far better when overclocked, a hexacore Phenom will honestly not make any noticable difference in games, since any game, as far as I know, only utilizes 4 cores maximum. Check out bencies, eventually.
A Phenom II x4 clocked to 3,8GHz will presumably only bottleneck your GPU around 2-10%, while an Intel i5-2500 will bottleneck it about 2-5%. All depending on the game, of course. Games like StarCraft II are very CPU intensive, and makes your framerates go down by 10-15 FPS when using a PII x4, compared to a i5-2500K.
So unless you're doing something CPU heavy like video editing or large image rendering, I wouldn't recommend an AMD Phenom II x6 at all.
My suggestion would be to wait at least a month to see what happends to be out there.
AMD's new CPU line, Bulldozer, is on our doorstep and arriving in june, as far as I know. Perhaps it will suit you better than any enthusiast CPU on the current market.Edited by p4p3r - 5/10/11 at 7:47am