Optimal video cards for GIS programs

Any old video card will work for the 2D display functions. The video card's 3D capabilities only come into play when using specific 3D GIS features such as ArcScene or ArcGlobe in ArcGIS Desktop. If you aren't planning on doing 3D visualization then it does not matter one bit.

I would spend the extra money on an SSD instead.

I used to benchmark cards against ArcView performance 10-15 years ago. A decent 2D card would perform at least as well as the high-end 3D cards, exactly as expected: panning and zooming around in a map doesn't use the 3D capability. I don't think this has changed any. (Two years ago, when fine-tuning a new workstation, I benchmarked the low-end Nvidia NVS 295 against the mid- to high-end Quadro FX 3700, costing ten times as much, and found the 295 was just as good for the 2D stuff.)

More interestingly, there have been moves to exploit the GPU processors in the cards for speeding up GIS analysis. Manifold was the first: they have built-in capability to use the Nvidia CUDA technology. Even the lower-end cards, like the cheap business graphics-oriented NVS 295, offer a handful of floating point coprocessors. The higher-end cards will get you up to 512 FPUs. You can install several of them if you want and get your raster processing done with a couple thousand processors at once :-).

I am aware of research proposals and small business startup proposals for developing similar technology for other GIS platforms, but have not seen any of them funded yet.

Aside from performance, something to consider for a GIS workstation is multi-monitor support. If you want to run three monitors, then this card supports it through "Eyefinity" technology. Just be aware that one of your monitors must support Display Port or you need a DP to DVI adapter.