Maya 2015 needs 10.8 or 10.9
so if you can afford it do get a MacPro you are off to a nice
do get the biggest Graphics Card you can afford. Also
the biggest drive you can get..
The CPU and the RAM can be upgraded as well as the
drive capacity thru Thunderbolt 2
you would need at least a 27 inch Screen - so the Apple Thunderbolt (1) Monitor might be a nice
You can max out the MacPro with 64GB of RAM... so buy as little as possible RAM from Apple as
they are expensive on RAM and you would not need more than 8 - 16 GB to start with anyway..
when you go into Rendering later on you will need more RAM then..
With a constraint budget i´d get an iMac 27 BTO with the biggest Graphics card and internal Drives
you can afford. RAM is user-installable..