650W great enough for two 4850's? and two 4850's on AMD board?

The power supply is sufficient, and of course AMD graphics cards can be crossfired on an AMD board, but only the AMD boards that have two PCI-Express slots and a chipset that supports it.

Post your motherboard and we can tell you, or look it up at the manufacturer site.

You should be good to go.

http://www.biostar.com.tw/app/en-u [...] p?S_ID=374

# 2 x PCI-E x1 2.0 Slot
# 2 x PCI-E x16 2.0 Slot (CFX x8)

Only runs in x8 mode, but shouldn't matter much if at all:

http://www.tomshardware.com/review [...] ,2095.html

"Only runs in x8 mode, but shouldn't matter much if at all"

With x2 3870's on a SB600 board that had 2x8 I gained 25% 3dmark and about 30% in game fps going to a board with 2x16. With something like 4850's I'm guessing there is going to be a good deal of bottle necked performance that you'll be missing... If you haven't bought your cards already might want to look at the 4850x2