Go for the 890 board; if it runs well, I wouldn't flash the bios later on when updates are available. I see more dead boards from asus than any other brand after trying a bios flash. I like msi's flash program, but still have to disable boot block and any pop up blockers when flashing.
If you are thinking about doing cf, choose the ASUS M4A79T Deluxe (or wait to the 890FX). If that point is not important for you, choose the ASUS M4A89GTD PRO/USB3, which is newer and has more features.
The M4A79T Deluxe isn't very good, an the other one have onboard video, that isn't good for gaming rigs.
If I were u, I would wait until tomorrow that comes out the 890FX mobos to check the price and the characteristics, and maybe with that the current 790FX mobos drop their prices a little more.
Also, we need know what other components do you want install in the mobo. RAM, GPU (Crossifre or not). Because don't have sense spend $200 in a Crosshair III or $250 in a Crosshair IV (890FX chipset) if u only want run a GPU.