I'm about to buy a new workstation. One thing I can't quite figure out is just how much difference in performance I would see between a Quadro FX 580 (one of the entry level models) and a Quadro FX 4800, or for that matter the mid-level Quadro 2000. As far as CS5 usage, how much do the higher end cards give you? I'm planning on 24GB RAM and still figuring out the fastest CPU I can get, but confused on how much I should worry about a particularly high end card. In the AE forums they're saying RAM and CPU are far more important than a high end card.
I can compare the high-end Quadro I have at work vs using PS CS5 on my home PC which has a high-end gaming card; I don't really notice a huge difference since having the Open GL on both alone gives you the few extras you'll need like rotate-canvas and working in what 3D tools PS has. I would say save the dough and go middle of the road... that way if you ever need any of the Adobe video programs you'll be able to take advantage of the mercury engine.
Although i never worked with much 3D stuff in PS, I don't think it would take a crazy card to get you the power needed. I think if your running a huge resolution on multiple displays it would help.
I have two screens running at 2048x1152 with 2 views of my Photoshop project (one fit to screen, the other zoomed in) and the 4800 works flawlessly. Never tried that with the lesser card though.