jeep lib is little? it's far larger than my jetta, and my jetta is a reasonably big car.. but that's just me i guess, from the size of the crap on the roads these days.

oh well.. on the topic, I had a discussion about building mobile tube amps with a friend of mine who has done design/build work for atma-sphere over the years. Vibration issues are the hardest part of tubes to fix.. a rubber mouted suspention system for the amp would be required.

Personaly, I find any good quality mosfet amp to be more than reasonable for a car amp. Mosfets provide most of the harmonic qualites of a tube, without the problems of tubes.

The bigest problem with your setup is the empeg, I had a long talk with a car audio system designer, and he did some research into the empeg's audio end.. while much better than a normal PC system, it has a long way to go to compete with some of the better quality decks out there.

doing the digital out, and getting an external DAC would probably be the best solution to really getting the best quality out of an empeg based setup.