Does ANYBODY know if AMD's 880G/890GX chipset allows for automatic or manual switching between onboard and discrete graphics cards for power savings?
No. Hybrid Crossfire has nothing to do with 'switching' between the onboard graphics chip and a discrete card one may install. Hybrid graphics works only with certian compatible cards (usually of the low performance variety), not all discrete cards. Hybrid graphics is a joke performance wise. I suggest you read the online User's manual for the MB you plan on purchasing and specifically the hybrid graphics specifications, what it means and what cards are capable of creating native crossfire with the onboard graphics chip. A single high performance card will tear a new one in any hybrid crossfire configuration.