I own an older Sundance 880 Optima spa. Bought it used about 10 years ago. Great tub, never a problem with it. Recently the built in sound system, which sounded quite nice, has failed. I need to replace the receiver component. Original equipment was a Poly-planar MRD 60. They don't make them anymore, although the local spa shop has one for $500! I would like to upgrade to a bluetooth unit with a working remote anyway. The original unit was pretty basic, essentially an auto receiver built into a waterproof case. Anyone have any ideas for where I could find a unit that would work in this application. I have no problem with installing it myself. Like I said, basically a car receiver.