no experience though. You mentioned you thought they would "drop in" and that's a major consideration. When I looked at Polyplanar I noted that the cut-out holes for Polyplanar brand speakers were not a common size used by any other maker I looked at. Bose also uses unique sized cut-outs. Other makers like Panasonic, Sony, Clarion, Pyle, Alpine, Kicker, JL Audio, Kenwood, Polk etc. use common size cut-outs. Mine was a new installation so I chose common speaker sizes that allow more options when they need replacement.

The other thing to look at is mounting depth. Make sure to wire them in-phase; for best sound quality you need to pay attention to polarity throughout the system.