My concern with the 160 is that it may be too far below your ears. I have mine exactly at ear level and it sounds terrific. If I drop it below ear level, there is a noticeable change in sound quality and it no longer sounds as if voices are coming from the screen but rather from below it.
The in-wall M5 as you described won't suffer from the problem above. In my listening tests, the M5 does not sound as big as the 160 but its off-axis response is better than the 160 particularly as you fan out 25 degrees and greater. The M5 also has higher fidelity bass even when crossed over at 80Hz particularly at higher listening volumes.
I'm not sure if Axiom makes an in-wall 160 and what the specs for that might be.
