Which graphic cards? Nvidia Quadro Fx3800, 4000 or Fx5600?

Hi Guys,

I've got a Dell xps 8500 with i7-3770 @3,40GHZ 12GB RAM and I'm struggling with AE C6.

Quadro FX 3800 http://www.nvidia.com/object/product_quadro_fx_3800_us.html

Quadro 4000 http://www.nvidia.com/object/product-quadro-4000-us.html

Quadro FX 5600 http://www.nvidia.com/object/quadro_fx_5600_4600.html

Which of these cards would be bring me the most value?

Thanks for your help.

Rgds