Recommended NVIDIA graphics cards for Alienware Aurora R1 (2009 model)

I recently purchased a very clean Aurora R1 (built October 2009). Has the following specs (as given by the seller):

Water cooled Intel i7 920 8mb cache eight core gaming PC running at 3.2ghz factory settings.

Has a Radeon 6950 series graphics card with a 6970 BIOS installed to enable the switched off pipelines. 

24gb Gskill ddr3-1333mhz Tri-channel

I would update the graphics card in the future if I was keeping it. The PSU is a high power unit and has 2x6pin & 2x6/8 pin so 4 graphics card power cables in total. You can run graphics cards in tandem (SLI).

I am getting blue screens with the Dell Radeon graphics driver and would prefer an NVIDIA graphics card. Can anyone kindly recommend a decent card. I am not a gamer, but want to use this PC for scanning old photos/slides and video editing.

Will any series 400 or 500 work please?

Many thanks in advance.