I wish to use the FM2 A10 5800K with integrated HD7660D & hybrid crossfire with 7750 4GB or 2Gb dedicated card... Can this work?
It doesn't appear so. Based on AMD's web site
, the best card you can Hybrid Crossfire with is the HD6670.
Also can more that one card be used to maximize performance?
The second PCI-Ex16 slot on both of those motherboards only runs @ x4. I wouldn't try to Crossfire/SLI using a board like that. To my knowledge, you cannot set up a hybrid Tri-Crossfire set-up (APU + two Discrete).
If you want Hybrid Crossfire with that processor, you need a Radeon HD6670 discrete card.
If you want to set up Crossfire, you need a motherboard that has at least two PCI-Ex16 slots where both slots (with cards installed) run @ at least x8/x8 (not x16/x4).