Tommy, your replies clear up some questions nicely.
Regarding the case, if your intention is to deliver this as an item to put in/near/on a speaker, I would think that the best decision is going to be the case that performs best in the worst case scenario, as anything else then would work fine by default. In my mind, this makes the case decision the one that makes attaching the amp to the largest number of possible speakers the best?
Considering the height of the case isn't much more than the depth of a pair of binding posts with banana plugs attached, the cube case looks smaller in footprint to the flat case, so it would then follow that it would fit behind a larger (in this case, physically smaller) number of speakers unobtrusively. An idea that just came to mind - why bother with the binding posts on the amp at all? why not just terminate with a pair of pigtail connectors, or even a pair of screw down tabs coming straight off the boards, eliminating the binding posts on the amp themselves as a performance bottleneck? Also, if this is the intention, mounting tabs on the cube case similar to the flat one would maybe be a good idea as well?
Completely my own armchair opinion here, but although I admire and am intrigued by some of the out of the box thinking going on here (from expanded applications to performance improvements), I think you might be shooting yourself in the foot heading completely down this road form-factor wise right out of the gate.
I don't know exactly who the target market for this amp is, so I won't presume too much, but going too far off the sociological norms of the target customer in how the product is presented is a quick and easy way to have to fight an uphill battle for mindshare, even before a customer takes a chance to see how good your product really is. It would be a shame for someone to not even give these amps a chance just because when that person would think about just unplugging their current amps and put the M's directly in place of their current gear using their current stands and cables and so on, things didn't just look or hook up "right", if that makes any sense?
Maybe starting with a more "traditional" form factor at first, then expanding to something more exotic would be the wiser course for a new product? There are a lot of companies around here that do very well with lower cost prefab casework that looks very nice, and brings the overall production cost of low-volume manufacturing runs down considerably. I know no one wants to be a "me too" company, but again, depends on the big picture goals.
Cheers! . . . and I think it is very interesting that the same single amp scales up power-wise based on power supply alone. One amp, with multiple power supply options basically making multiple amp models, is an interesting departure from the traditional amp marketplace. Nice!