Yes the magnets are very strong. So much that if it was magnet to bare metal you woudl have to pry it apart with a screw driver. But with the magnet behind the felt, it holds just right.
Just curious, how does the Nexus work with two bluetooth devices, so I saw you were using bluetooth volume, and OBD2 bluetooth adapter, do they both work at the same time?
Do you NEED the x-over? The Bose symphony II amp should be enough?