[H] Switch from ATI 5750 Crossfire to NVIDIA what?

[Winterlight]

I am currently running two Sapphire ATI 5750 Crossfire video cards 
driving three monitors....one 30 inch and two 24 inch monitors. I 
have the three monitors connected to a single video card, and I have 
the second one plugged in for Crossfire support. I have been running 
this since 2008. I rarely play a game.

I want to switch to a single Nvidia card so I can get two of my ports 
back and get NVIDIA CUDA support as I use TMGEnc encoding software. I 
don't want to spend a lot of money, or generate a lot of power draw, 
and heat. I would be happy with similar video performance to what I 
have now ...but in a single NVIDA card...but which NVIDIA card is 
similar or the best value?

Thanks!