SLI is a technology available only on NVidia based video cards.  It allows two paired video cards to run as one.  These cards must be identical.  SLI exists only on PCI Express mother boards with SLI enabled.  One major drawback is that SLI supports only a single monitor.   

During testing testing it was found that SongShow Plus and SLI are not compatible.  Running in single monitor mode with SLI enabled there were a number of problems that would prevent SongShow Plus from being able to display a program in a service.  Simply unchecking "SLI Mode" in the Nvidia drivers does correct the problems but the video cards will no longer fucntion as a single unit.

The lack of dual monitor support and the increased cost of an SLI system out weigh most, if not all, of the potential benefits that SLI could have provided.  SLI based motherboards cost on average $40 more.  Add to that the cost of  buying two $200 plus video cards and you've spent $440 that could have been used to just buy a better single video card.  

As of yet ATI’s Crossfire technology has not been tested.  However we do not expect it to provide any different results and are not currently recommending it as a solution. 

(DI008)