No long description to give here really, just a very overdue update on the boombox build, I finished it early this summer (although I still haven't gotten around to painting it but I'm going to share a few pictures. The sound quality is pretty good, definitely better than most store-bought boomboxes.
I should note that it currently uses a 7.2 Ah battery that's good for about six hours of constant use if I don't turn up the volume too much, I'm considering getting something a bit more durable for next summer.