eh...
no, just plain no.
go with two GTX570s SLId instead. More bang for the buck. They're neck to neck but the 570s are cheaper.
http://www.tested.com/news/radeon-6990-vs-radeon-6970-crossfire-vs-gtx-570-sli/1985/
And if I had time I'd find 2 fine tuned 560TIs doing almost as well but I wouldn't bother with those imo.