Picked up two HD 5870s to run with the one I already have for triple Crossfire X.
After reading all the reviews out I decided I'm not interested in nVidia's offerings this go around.
I'd rate the 480 as a 6 and 480 SLi as an 8 on a scale of 1-10. Triple Crossfire X should be around 480 SLi performance often. Below is an old review of it that was done last year in October.
The two additional 5870s were 395usd a pop from ZZF with free shipping.