Hi I run pro tools and logic on my macbook air, and 2 iMacs. I had read issues with El Capitan so installed the update on just the older iMac. Logic working 100%, pro tools okay once i updated the drivers.
My old 1st gen m-box is still working if i use an emulator driver and the quality is ok, maybe not as good as it was but I've since moved on to a focusrite scarlett.