I haven't been following this thread too closely--If Sea Islands is used, are we looking at a low-end or mid-range GPU from the R8XXX family?
My guess is low end like a 87xx GPU, which should be in the performance region of a 78xx Pictrain GPU, but with much better power numbers, probably similar to a 77xx series (~75W for entire GPU card).
I can easily see a 75W GPU + 35 W CPU + 40 W for everything else.