Definitely a lot of questions left unanswered here. When you say the computer will be external, are you talking about the guts of the jukebox itself, or just the server that is holding the songs? You definitely need to have the workings of the juke self-contained, if you're going to put the work in to build it you need to take the next step. Also, with a case that small, how are you going to include the amplification hardware you need? Are you thinking external for that too?