I would check both your BIOS and your display settings (NV control panel) and make sure that SLI is enabled on the Sager. If you believe notebookcheck.net, a single GTX 280M should score around 11 or 12K in 3dmark 06 depending on your CPU (they had Quad cores in their test laptops). So it sounds to me like only one card is enabled.
Single card benchmarks: http://www.notebookcheck.net/NVIDIA-GeForce-GTX-280M.14558.0.html
Dual card: http://www.notebookcheck.net/NVIDIA-GeForce-GTX-280M-SLI.17191.0.html