As AR is CPU intensive rather than GPU, any thing with a fast multi core CPU say 3.4GHz or more, plenty of RAM (you can never have too much of that!) and preferably with a Fusion Drive or Flash Drive (Solid State Drive) should give you a very zippy AR experience.
All the above could be configured in a new 27" iMac if you want to stick with Macs.
Maker Of Replica Macoys
Techie Stuff:
ArtRage 5.0.5 ~ 15" Macbook Pro + 22" HD Monitor ~ macOS 10.12.6 ~ 4 Core i7 3.1GHz CPU ~ 16GB RAM ~ Wacom Intuos4 M and a Spyder4Pro (to keep the colours true!)