This could be another option if you don't mind the work involved....
https://www.subaruforester.org/vbulletin/f77/install-8-sub-stock-location-3540/
No idea about that Bose speaker you posted.
https://www.subaruforester.org/vbulletin/f77/install-8-sub-stock-location-3540/
No idea about that Bose speaker you posted.