actually, it's the ones with the cooling fans that can be mounted virtually anywhere in most cases. i never recomend box mount, though i have done it before, and it happens all the time without problem. biggest problematic amps are ones that have poorly secured parts and/or large flex planes. i've seen allot of buzzing torroids, broken transistor legs, dry connections on caps, but many amps also factor these problems out in the design. i have not actually seen inside the new mbquarts, so i cannot say how duranle it will be, but all i can suggest is to choose a spot that is the most rigid on the box, like near the edge, or a known brace, rather than center-plane.