If you're thinking about a mac pro, you're probably going to be spending a lot more than 3000 (not including the monitor), especially if you get a quadro... that's one reason why I decided not to get a mac pro... overpriced, though they do have a certain appeal.

Also, there's no single optimal setup for Maya, that I know of, lots of different configurations will work great.

Couple ideas to start looking, you could look at a core i7 setup, with DDR3 RAM, 6 GB or 12 GB. Then you'll need an X58 motherboard, I've heard ASUS and Gigabyte are good, but people's experiences and opinions differ.
Apparently CPU speed and RAM are important for rendering, and having multi cores helps too. i7s like the 920 have 8 virtual cores (4 physical cores), which seems to be good for the price.

Make sure you check reviews on the components you're looking at...

Hope that helps a bit.