AFAIK that board will support the 4670 and 4770 in Crossfire but I am not 100% certain, ATI has yet to update its compatability chart.
If nobody here knows for certain, I would suggest you contact ATI or post a question on their Forums, I would hate you to buy it only to find it is not what you want or need.
The board you have linked to is open box, before installing it you will have to download its drivers and software from the Asrock site and burn them to CD/DVD so they can be installed-I know this is obvious, but it's an easy mistake to make;)