Im not very familiar with the other two programs but here's the thing. While the GTX series rules AutoCAD 2D and 3D drafting, Maya performance on GTX series cards is terrible. Zbrush does'nt appear to be too worried about what you use and Nuke uses OpenGL and likes CUDA
http
/www.tomshardware.com/reviews/best-workstation-graphics-card,3493-12.html
The flip side is workstation type GFX cards are usually poorly suited to students for entertainment (read gaming) . I would suggest you discuss these needs with your college administration or professors before deciding either way
Your budget is around $1350 and my typical suggestion, given your stated needs, would be to find a Clevo distributor and have the system built to your...