Current Equipment (taken from vw.com specs.):

Monsoon Sound System 8 speaker with amplifier, Premium IV radio with AM/FM cassette w/ 6 disc CD-changer, trunk mounted.

As far as budget, it doesn't really matter at this point, I just want to get an idea of what can be done and maybe rough estimates as to how much it will cost me.

Ideally, i'd like everything in there now to continue working, and have the empeg work with as much equipment as it can. My reason for this question was to get some insight as to what I can do with this equipment, what options I have, etc.

Any other info needed?

Donato