Is this the motherboard you are thinking of?
GIGABYTE - Product - Motherboard - Overview - GA-MA790X-UD4 (rev. 1.0)
That board has an
AMD chipset which does not support SLI (and I wouldn't count on it supporting more than one nVidia card at a time). Use ATI cards or swap out for an nVidia-based motherboard.
Interesting benchmark you show there; if I were to guess it would be beta BIOS or the fact that the HT link on a Phenom 920/940 is clocked lower than that of a 9850BE (1800 vs 2000 IIRC?) You'll be able to make up the gap if you OC the HT link as well (by either changing NB/HT multi or raising the reference clock speed from 200 MHz)
EDIT: Are you choosing between the 6000+ and the 5600+ for now? I'd go with the one that is
65nm, so that's the 1 MB cache (your heat sink with thank you for it).