Based off the Beta, even very GPU powerful systems like SLI/Crossfire setups aren't CPU limited with a 'modern 3.2GHz quad'. Basically any modern i5 or Phenom X4 or X6 will handle the load pretty well - you do want a quad-core, and a reasonably fast one at that but absolutely agree it's not worth prioritising over a good graphics card, I wouldn't buy any FX series (Bulldozer) CPU's as they're fairly average, and give worse performance in modern games than their predecessors (Phenom II). As you seem to be budget restricted a Phenom II X4 955 or X4 960T would be the ideal buy, coupled with a 970 series motherboard (as long as you don't plan on Crossfire later on down the track), and an HD 6950 as everyone else is recommending.
Note that not all HD 6950's can unlock - some have BIOS' that can't be flashed and some allegedly have their extra cores laser-etched out. From experience if the price difference isn't too great it's worth hunting down a reference 2GB card with a dual-BIOS switch (this allows you to use a backup BIOS if you bork your flashing of the primary one). I personally found I had temp and artefact issues when using a 6970 BIOS, but you can easily flash with an 'unlocked' 6950 BIOS then use a program like Afterburner or TRIXX to overclock your card - I've currently got my HD 6950 @ 910/5600 MHz stable with all 1536 shaders unlocked (as opposed to 800 MHz/5000MHz with 1408 shaders on a stock HD 6950), which gives a > 20% performance boost, is faster than a stock HD 6970 and is pretty typical of unlocked cards).
Anyway if you do decide to go down that path, you can identify a 'reference 6950' fairly easily, they should be a 2GB model and look like this (just with the manufacturer's sticker on it):
So yeah to sum up, an X4 955/X4 960T and 2GB (reference if possible) HD 6950 system would own. 4GB of system memory is fine for BF3, but TBH it's so cheap I'd just grab 8GB of DDR3-1600 CL8 memory for future-proof'ness. Built a friend a system like this last month for BF3 and it runs it fantastically.
Edited by philo-sofa, 10 November 2011 - 06:09 AM.
i7 860 @ 4.0Ghz | Prolimatech Megashadow & 120mm Gelid | MSI P55-GD65 | 8 GB G.Skill DDR3 1600 CL8 | Sapphire AMD HD 6970 (flashed from HD 6950) @ 910/5600 MHz | 2x 160GB Intel 320 Series (RAID 0), 1.5TB + 2TB Seagate | Corsair AX-750 | Silverstone TJ10B-WESA | Samsung 2443BW | Logitech G19 | Logitech G500