here is what I am thinking. Based on Don P's work on his grandson's ? spider.
I'd like to find a stereo bluetooth receiver, and mount it probably under the dash. These are small boxes that can run on 12V and draw low power, so I would run it off a switched fuse (I think there' s a spare). It connects via bluetooth to my phone, which then becomes the audio source. I'd run the line-level output of this to a 12V powered amp mounted somewhere (I,m thinking trunk shelf) and then run wires from the amp to whereever I put the speakers. Thinking two behind the seats, and maybe two door speakers? Dont know yet. Again, I'd run the amp +12 off a switched circuit via a relay under the hood. Don had found an integrated bluetooth amp (JBL) for about 150 bucks, but now its NLA and the cheapest I can find is a Kenwood one about $250 bucks. I was hoping to do this for less ----