The asus Crosshair III Formula is the best AM3 motherboard with the MSI 790FX-GD70 mainly for overclockers, and after that is the ASUS M4A79XTD as the best bang for the buck, it can do crossfire, have overclock cabapility. I have a ASUS M4A79XTD really my only concern about it is that it doesn't have the onboard power switch and doesn't have the cmos clear button, have to clear with the pins.
That's my opinion. I would choose it from your budget depending on which one is closer to it. How much are willing to spend on the motherboard? If it is $200 than I would say for sure the crosshair III formula, if it is something close to $170 than the MSI 790X-GD70, if it is something close to $100 the ASUS M4A79XTD EVO
So those are my suggestions, hope it helps