I think a very good head unit / amp / speakers will provide the basis for a solid system. If you want to play MP3's and other trendy media (MiniDisks) then find a unit that will interface with a standard digital feed. I know a number of people using iPods to feed MP3's to their stereos.
My ideal system would be a good pre-amp head unit, a clean amp and some tight speakers. Then hook in a cd changer or mp3 player or disk drive unit (if 1G SD chips are $250 or less) no need to have moving parts IMO.
Leave all the disco lights and other bells and whistles for the kids who think that is cool, because it is. It just isn't really necessary for good sound.

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Bryan Harter
1992 500E Smoke Silver
2002 CLK55 AMG Cab Silver/Black
2001 Harley Fatboy - Pearl White
2004 F150 FX4 Silver/Grey
1969 GTO Liberty Blue
1956 F100 Black