I found a somewhat halfway decent review (didn't cover exactly what I wanted, but good enough) at hothardware, at least in reference to Premiere. It's a review primarily of the Quadro CX w/1.5G RAM (~$2,000 at the time of the article) and the QuadroFX 4800 w/1.5G RAM (~$1500), and a 9600GT w/512mb RAM (I'm guessing ~<$100).
http://hothardware.com/Article...station-Graphics-Card/
Benchmarks include Cinebench OpenGL Rendering, Premiere Pro H.264 encoding, 3D Studio Max, Maya, a whole bunch of Spec Viewperf OpenGL tests at various resolutions, and finally 3D Mark and Crysis benchmarks.
The two Quadros tested are based on the GTX200-series GPU, and the 9600GT is based on some older GPU (somebody else can chime in on that).
The 9600GT holds it's own in the H.264 tests (scores nearly identical). The exception is the QuadroCX which has the RapiHD plugin that is CUDA based and is nearly double the speed of anybody else. Clearly, this is CPU bound.
3DSMax is close enough where I wouldn't pay the $1400 premium for a quadro.
In Maya the 9600GT gets blown away, so the cost is worth it there.
All the Spec ViewPerf test crush the 9600GT, so the cost is worth it there if those benchmarks correlate to something you might do with the card (maybe CAD software?).
In Crysis, the quadros are better (about 25fps vs 35fps). I put that on the fact that the quadros tested are GTX200-based which it should only be expected would beat up on the 9600GT.
What I would like to see, which as far as I can tell no one has done, is a comparison of performance in Adobe programs using a cheapo GPU, a mid-range GPU, a high-end GPU, and their corresponding alternatives in the workstation class. Just looking at what it is the GPU is being asked to do I can't think there would be much difference between any of them in tasks like zooming, panning, decoding video. Some of the special effects filters like depth of field and blurs in After Effects I can see benefiting from a faster card, but not so much that I would rather pay a double, triple or even quadruple price premium for a workstation class card. Not for use in Adobe software. If you're doing CAD/3D work, then thats a whole 'nother story.