But seriousness in perspective, running SLI is pretty noisy and power consuming. (Unless you can space the cards 3-4 slots away from each other --- ie: 4-5 PCI-E slot board)
The single card, Dual-GPU solution is typically quieter and less consumptive.
Besides, the kind of person buying a monster like that wont be doing it the injustice of trying to stick it in a micro case