I have sold all of these decks, and owned decks from 4 out of the 5 companies: Eclipse, Alpine, Clarion, Pioneer Premier, and Nak... Of the high-end units offered by these companies... I can tell you this about them from my own experience.
Eclipse - Sounds great, reliability used to be an issue, but I heard not so much anymore. For the ones that dont have any problems, they seem to last for a very long time. I owned the 55060.
Alpine - Good all around, not really a stand out, but not left behind in any regard. The laser on Alpines seem to go out slowly, but only after about 5 years with everyday use it seems. I have owned the 7909, and the 7842.
Clarion - Used to be the heavy hitter in the high end decks. A few years ago, I would of said that the high end Clarion Pro-Audio decks were the industry standard, but now they seem to of gotten out of the high end audiophile competition decks. They are very reliable and sound great. (I own the last of the Clarion Pro-Audio audiophile decks, DRX 9675z.
Pioneer Premier - These sound really good, but most of all have awesome features. The reliability of the unit is great. The buttons wear out prematurely though. If you use a remote, then problem solved. I have not owned a premier unit.
Nakamichi - I had one of the units that had the analog volume control. The nak sounded wonderful, and was fine all around. It did not offer too many features, but was focused on sound quality and good reliability. I forget the model # I owned.
When it all comes down to the purchace, I would audition it at a good shop with a good sound board (some sound boards can make even the best cd player sound like a $5 garage sale 8 track player) and get the unit that best suits your needs; reliability, features, sound, flashy lights [jk]...
Have fun!!