Crossfire doesn't work that while right now, because of the drivers. Crossfire with 3 cards is much worse. 2-way SLI works pretty good right now. So you can pay $1320 and see crazy performance, or pay $900 and be disappointed.
The other possibility, if you're a bit short on money would be to go GTX 770 2-Way sli, which also performs great, and has a better price/performance ratio.