It's easily worth $500 in my eyes. The Alpine 1507 amp retailed for over $900 when it was new, it's the largest 2 channel amp they have made as far as I know.
I don't know much about MB Quart speakers (as far as model #'s go), but I would guess that's a component set. Check the crossovers and see if they have outputs for 3 sets of speakers.
Used audio equipment is never that easy to move, so you might see if you can get some wiring out of the guy too.