I got a Sapphire 3850 here. Personally, i think it runs a lot better then the 4670.
Its paired up with a Opteron 170, 2gbs of ram, and an older 32gb raptor. All running on a Asus A8V deluxe motherboard. Running on a thermaltake 480watt psu. I only pull around 320watts at full tilt according to my little watt meter fyi.
Its a great card and can does fairly well. I can run crysis with medium to high settings. As well as farcry. When I overclock the cpu from 2.0ghz, to say 2.9.... FPS dramatically improve.
So keep that in mind.
Also, I had a socket 939 single core 2.2ghz newcastle core running on a gigabyte sli mobo with a gtx260 a little bit back. Crysis was unplayable at times. CPU power just wasn't there.
Good Luck.