Well i've devoted a core to my two 3850s now and the results are pretty impressive
on the three remaining cores [at 3.1ghz] you get about a WU every 20 hours. Not too shabby, there's better performance out of C2Qs but what makes up for it is the crossfire'd videocards pulling their weight
GPU work Units go fast.
I get a percent every 2 minutes.
In an two hour work unit worth between 100 and 200 points [well 98 and 196] that adds between 1200 and 2452 ppd to my total
that on top of the roughly 1900 ppd i get out of the quad already, you can build a nice machine with a radeon or two.