It's been a while.
For raw speed, the new radeons are probably the best, but a 3DLabs Wildcat VP series will have better image quality and stability. Quadro is probably the most powerful consumer/private workstation card. Going above Quadro would bring me back to 3DLabs, for their Wildcat IV or better (and muchos dinero).
I'm not sure if Maya runs best in DirectX or OpenGL. That makes a difference because if he needs good OGL then he'll be better off with a workstation card.
At half the price of most "pro" options, I would certainly consider a 9700 at least as an option.
BoB said this; "Game cards suck at CAD, CAD cards suck at Games." The second part is far truer than the first. Real pro CAD cards are designed with no consideration of price and by the time gamers can afford them, they should really be melted down for parts. Game cards work fine for CAD as long as the app runs fast in DirectX, they're just a little rougher around the edges.
Ask him his budget, after you max out the CPU/RAM, spend the extra on a pro card. If you can't max out the system with the budget, get the Radeon.