If you want the best head units around, there are really only 2 brands to consider. Denon and McIntosh. Both are hard to find and cost an arm and a leg, but you cant beat the quality.
I used to do custom installs when I was younger, and got to play with a lot of different units. I ended up with a Denon in my first truck; totalled the truck, put the deck in a new one, totalled that truck, replaced a $2 plastic piece to allow the CD's to come out. After 6 years, changed to a newer MP3 deck (Rockford Fosgate) and it got stolen. Put the denon back in until insurrance check came in. Got a new car, put the Denon deck in after the deck got stolen on 3rd day of ownership. Still have the Denon sitting in the garage for another situation. Damn thing is 14 years old, and still has better sound quality than any other deck I've ever owned.
Well, back to building my entertainment center, battery is charged!