This is at the Nvidia Forums here http://forums.nvidia.com/index.php?showtopic=172243
Note: Be careful with the extensions on GPUs. The extensions often denote a totally different GPU. EG the GTX460SE and GTX560Ti are not SLI capable with the GTX460 and GTX560 respectively.
So unfortunately I would have to say NO you cannot sli the two together.
Sorry about that.