I decided to put the amplifier in the same cavity as the glove box with the head unit in my 210, and to modify one of the two plywood carpeted panels to accommodate wiring reaching the exposed amplifier through the carpeted plywood wall. Here's a photo showing the rear of one of the new speakers, the location of the amplifier, the new speaker wiring, and some of the wiring from the head unit to the amp. The "front" amp output goes to channels 1 and 2, for the bow, and the "rear" amp output drives channels 3 and 4 for the cockpit as well as channels 5 and 6 for the rear cockpit via y-adapter cables. The speakers by the feet of the captain's chairs were the easy ones as there was no upholstery - just a hole that had to be enlarged by maybe 1/4" all around to accomodate the Roswell R1 speakers being larger than the factory-original Kicker KM61 speakers. I bought all white Roswell speakers, so they blend better with the white fiberglass but stand out against the charcoal fabric in the front and rear of the boat. Connectors on the new speaker were Amphenol waterproof connectors, and so I ordered appropriate mating connectors from Digi-Key and soldered the pins rather than buying a specialty crimper. Part numbers were 889-1206-ND and 889-1207-ND, which are the male and female versions of the connector. Holes for the speakers were enlarged by tracing out the larger sized hole using a template and a Sharpie, and then carving out the material to the Sharpie line to make the hole bigger using a Foredom TX tool (like a big Dremel tool) and carbide-toothed burr bit. Rough edges were smoothed over with a cordless drill and 2" sanding drum, and upholstery was peeled back to expose the fiberglass in places where the hole openings were upholstered previously. I used 3M Super 77 spray adhesive to reattach the upholstery when done and fold it around the hole opening because it's what I had on hand.
Although I had to enlarge the holes for the new Roswell speakers to fit, the four screws to mount them mercifully lined up exactly with the holes for the Kicker speakers and I was able to reuse the old screws and screw holes without any modifications. The speakers liked up perfectly square despite looking a bit askew in the below photo, and a rotating trim ring snaps on to cover the screw holes.
More details to follow once the 1ga wire for the battery, 4ga wire for the amplifier power, and other bits and pieces arrive from International Marine, who had the best prices on heavy gauge copper wire...
