The older Quantums were apparently very, very good, one of my (unfortunately no longer) reps worked as a tech at Quantum for years and has a lot of time for them, but he said there are issues now as a lot of the bits are made in China.
One of the places I used to do work for had a number and one only ever broke down and all it was was an external thermal overload on the compressor. (which is a know fault with the older ones)
