as far as a basic setup is conserned id go with a p1900 for the power supply. it powers 1 screen and your mac. your multi screen setup will be a bit more tricky... a case for your mini just depends on you. a lot of people just stick it in their glove box with no problem. if your just wanting music and movies you could just use itunes (but few would recommend that) there are a number of good front ends to chose from in the front end section of the mac forum. all work with a touch screen but some work better with a external controller. just try em out. it all comes down to your preference and what features you want. checkout Neon Boombox we only have music working for now but movies will come shortly.
hope to see some install pix soon!
good luck and hope this helps!