Hi digs,
I did the double-blind listening tests to the in-cabinet Axiom models and I assure you there is no sonic compromise with the M80 and VP150 in-cab models.
The VP-180 is, of course, stunningly good--Axiom's first no-compromise center channel and I've not heard better at any price.
I really encourage you to somehow work the QS surrounds into your setup. In-ceiling speakers really don't work well, partly because human hearing is acutely sensitive to direction and timing for lateral sounds and those in front. (Notice the angle of the pinae--the external part of our ears.) We don't sense directionality nearly as well from above or directly behind us.
Think about if you hear an aircraft flying over you somewhere outside. If you do NOT instinctively turn your head upwards so your ears can help locate the position of the sound, you'll have trouble figuring out where the plane is.
The same applies in directional cues mixed to the surround channels in 5.1 soundtracks. They're intended to be reproduced from side channels, not above.
Regards,
Alan
