I run ProTools on a Mac. PT came with an Elevenrack that I have been using as my main interface. I also have a Helix which I prefer for guitar tones. Recently I was given a Focusrite Saffire 6 USB and a Presonus Audiobox 44VSL.
I would love to have all of these options available via an Aggregate Device. I have set one up as such.
Since setting this up, I have had a couple of glitches. I don't know if it is just a coincidence or if having 4 units is actually hogging resources.