1987 944 Providing Power to Subwoofer

My 944 doesn't have seat heater but has a 25a fuse.  I plan to remove the seat heater fuse and install a fuse tap that has two fuse slots: one for original and one new 10a circuit.  Probably will use a 10a fuse in both slots.  Looks like I need to drill a hole in the fuse box below the lid and add a rubber grommet to seal the new wire to the subwoofer.