Main purpose for this machine is as a workstation for running Maya and ZBrush. My budget is $2000 max.
I was also considering the SAPPHIRE 100259-1GL Radeon HD 4870 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card for $200 (http://www.newegg.com/Product/Product.aspx?Item=N82E168...). It would save me some money but I'm not sure how it will perform with Autodesk Maya 2009 and that is my main concern. The Quadro cards are qualified and recommended for Maya so I'd rather be safe than sorry.
You are right about the video card. You need those workstation drivers. It's sad really because the actual hardware of a gaming card is superior, but you have to pay those devs for the specialized drivers.