Using external looping station with Mainstage?

Considering I am simultaneously using three different instruments within my set, and doing everything at set levels, I am trying to reduce usage of CPU. I am using three controllers currently. Two keyboard controller's, one for bass and low register pads, the other for keys/strings/synth/etc., and an MPD for drums.

My plan is to use looping stations with the drums and both keyboards independently. I will likely be purchasing at least two loop stations, or one with versatility and multi-tracking capabilities for at least four independent looping parameters. The fourth not mentioned would be for a vocoder that I plan to purchase.

I would like to get some input on this before making a huge purchase. I don't have a Mac Mini so my MacBook needs some breathing room to be reliable on set!