the nvidia on the name of that MB, should give it away that is not crossfire compatible, since crossfire is a AMD/ATI technology. An in my opinion not worth if your main intent is to 5 box something like WoW.
Consider the following:
- In order to fully utilize TRI_SLI you will need 3 top end nearly identical NVIDIA cards
- Most single computer multiboxers use two monitors (or more) as to have screen real state for all five instances
- Dual SLI support for two monitors was introduced recently, possibly the implementation is not very robust yet ;-)

With $2800 you could buy two computers and play 5 accounts on each ;-). Bottom line is, for multibox WoW it is overkill, and there is nothing wrong with that. The system will last you a long time and you will be able to play graphically demanding games such as far cry 2 and whatever is next. But if this your intent I would suggest additional research on MB/ Graphics card combination ;-)

Edit:
Read some of the comments on the new-egg page for that motherboard you list. let me paste some excerpts:
" nvidia really did a job with this one....constant freezes regardless of modding the (very messed up) default voltages"
"Very unstable. You should be happy if it runs a for a full day without freezing. Typically, 1-5 freezes a day."
"It has had random freezing since I got it. I have tried everything."

These are from 3 different folks all on the main product page (i did not go searching for them). I am sure there are people who had better luck with this board. But that should set some alarm bells.