[Michael Carnes]

I have the same Mini as one of my test machines (still the best of the Minis), so I've tested every version from Mountain Lion on. El Cap really did have serious issues with graphics support (on all computers) and many DAWs were very draggy. I've had Sierra on this machine since the late Betas and it performs very well. Mountain Lion will perform equally well, but you'll have a much more secure system if you go forward rather than back.