I'm pretty much sold on this card, and Hybrid Crossfire sounds like a really cool idea. If this is incompatible, is there a way to use the Onboard GPU while just browsing internet etc. and then switch to the HD 5850 for games? Or should I just scrap the idea and get a different Mobo?
The hybrid crossfire is a feature to use a low end GPU with the integrated to get better performance. The HD5850 is a powerful card that does not need any help from the integrated. Having a board with integrated is not a bad option in case that the dedicated card fails, then the spare is right there.