Hi,
not to sure about this one so I'm not going to vote.
I know that you can enable crossfire using the on-board graphics and a ATI PCIe Graphics card on some of the other Gigabyte Mobo's but it has been a while since I tried (785 & 790 chipsets) and as the 890 is such a new board I'm not sure if an answer will be forthcoming (until some brave soul actually tries it). You also used to have a compatible Graphics card to match the on-board chip but I don't know if this is still the case.
When you find the answer let us know.