Could always get a TripleHead2Go as well!
It allows for a crossfire setup or even just a single-output video card to run three monitors up to 1680x1050.
Matrox Graphics - Products - Graphics eXpansion Modules - TripleHead2Go
Only problem is... they cost as much as another 4870 = ~$300.
Expect more about it in my upcoming review in the next week or so!