Years ago, I also would have said to get a Quadro. They could preview Poser with hardware shading enabled, and their generous onboard VRAM enabled high quality Vue previews. Three of my four workstations have Quadros, the two server midtowers have Quadros, and even my laptop has a Quadro. The blades only have a minimal video chip on the motherboard. TinkerBell has a used/refurb 12GB TitanZ; she's the only one which could do GPU rendering.

Now, even low-to-midrange gaming cards will support Poser hardware shading previews, and many gaming cards now have generous VRAM. Plus, if you get a GeForce card with lots of CUDA cores and 6GB (more, if available) of onboard VRAM, the GPU can be used to render modest scenes very quickly.

The nVidia GeForce 980Ti with 6GB is very capable and relatively affordable.

Be aware that if you switch from a GeForce to a Quadro, or vice versa, you need to diligently eliminate the old driver before installing the new driver - GeForce drivers and Quadro drivers are incompatible.

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5