Depends on which version of Max and what you are doing in the viewports.
Max2010 has hardware support for things like ambient occlusion in the viewports. Texture usage is not so bad in max viewports unless you set it to use real size in viewports then it can get large depending on how complex the scene. I tell people to get at least 512MB video ram , more the better if you use applications like mudbox. Mudbox can use 1GB+ video ram without trying too hard. Drivers I use are the standard nvidia release ones. When max started there were custom drivers that used Heidi but that is a dead api. Some vendors do have specialized max drivers called maxtreme.
http://www.nvidia.com/object/maxtreme_archive.html
I did not find the performance increase 100%, more like 20% and there are no drivers for 2010 yet. 2010 has issues with slow viewports that are unrelated to the cards used. Ask around and you will find lots of complaints about the slowness. Lots of people are still sticking with 2009 or Max 9 for that reason.
I think for most that use Maya, Max, Mudbox, XSI a good gaming card, 512MB ram + is all that is required. Stay with a driver that works, don't keep changing drivers to the latest as doing so can introduce problems. Most of the driver updates address gaming issues and can break 3d applications, so if what you have works, no need to update it.
Cards I use in daily work.
Quadro FX5600 - Driver 190.38 for win7 64 bit - would have not purchased had I not needed official support from Autodesk - something else to consider, have viewport issues ? First thing autodesk will ask is the hardware certified.
8800GTS 640MB - works fine, no issues with any applications, Driver 190.38 for win7 64 bit
Sometimes it is just the software.
An example is I can put a 10M poly scene in max and it updates at about 2FPS. Same scene in XSI, 19FPS.
