I would mount the maple piece first. As you had noted sheetrock can with stand quite a bit of load. A couple of the newer self tapping drywall anchors would work, they come in large enough capacities, but the maple strip behind the speaker would also be a nice touch.


Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70