CAD is a silly broad term (i should know, i worked in the industry) with MANY MANY different programs with MANY MANY different requirements. Even the samepeice of software could have low end requirements (if you were modelling, even modelling a whole CITY) and high end requirements for Rendering/stress analysis Ect..
Its all dependant on the software itself and the uses you are performing.
I used solidworks for my course, it wasn'tvery GPU dependant in all tasks. It was more RAM focused (especially with rendering) but from the looks (and what people have told me) about Maya its VERY GPU focused and Less (though its still important) to do with CPU power..
Basically, if i used a rig that was happily capable of running olidworks/NX/inventor for Maya it would be TRUELY awful.. Due to the different requirements andhow the program is built.
That is why a lot of workstations come with Xeons/Dual Xeons and a host of Professional GPU's (and lots of RAM) to cover ALL their bases...
and this is why you are recommending a higher budget equipment, what you have said is from a very pro focused.
trust me it is not needed for a student.
Currently my work uses:
AutoCad,
Inventor
3Ds Max
everyting is fine with those and really if you really think cpu is not a problem then you can up the gfx and lower the cpu to i3