As PAGAN mentioned, if you can swing it and you decide on Nvidia, the 260 is a great choice. I know this is an extremely popular card with the pro's on the Polycount website, people who work in 3D, day in and out for a living.
I myself splurged with the GTX 285, which was probably overkill, but I was building a new system anyway so I decided I might as well go balls to the wall and have a smoking fast system that won't choke on me no matter how hard I push it.
@ Josh Mooney: I used ATI from the days of the 9800, to the X850, to the X1900. This is when shader model 3.0 was becoming the standard and ATI was slow as hell to adopt it. And from other Max users, I hear they still can't use the SM3 hardware shading option in 3ds Max, as well as the DXSAS shader model 3 shaders, which show as just red wireframe in Max when using ATI cards. Maybe someone with an HD-series card can prove me wrong, I'd love to hear about it. I'm not an Nvidia fanboy, I just need to use what works.
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"bond1 - You see this name, you think dirty."