Mac mini expansion Graphic card

I have a mac mini (late 2012) i7, 16gb ram Vengeance graphic card intel HD4000.

I buy recently a thunderbolt expansion PCIE whit support a graphic card PCIE 2.0 16x whit space for Full leght card.

I have dubts about what graphic card gona give me the best results for using the Unreal Engine 4 UE4 or Unity3D, and Blender.

My badget cover a Nvidia Quadro K4000 3gb or ATI Firepro W7000 4gb. Any recomendation? What professional graphic card can be better for design games in 3D?

Thanks.

For doing games you need a gaming graphics card, not Quadro or Firepro, those perform poorly in game engines.