Hello:

I've replaced my non-nakamichi head unit on my LS400 with Kenwood DDX7015 (absolutely awesome). I'm wanting to do the same on our LX470,but the LX470 has the Nakamichi system in it. I don't want to lose the sound quality of the Nak system. Can anyone shed light on whether Nak system is after the amp (so, theoretically no loss in fidelity) or vice versa?

Thanks in advance!

 

Nakamichi has been making headunits for Lexus since they first appeared in the early 90's. The Nak system in an early SC or LS is actually a better quality, better sounding system than the newer Lexus Nak systems. In your LX, of all of the components (speakers, amp, headunit), the one to keep would be the headunit. The amp is completely expendable, any decent aftermarket amp will easily outrun it. The speakers (really crappy) are also easily replaced with decent quality aftermarket stuff. The CD changer is actually made by Pioneer (for Nakamichi/Lexus). The headunit, while the best quality piece of the system, can also be replaced with a good high-end aftermarket unit (Alpine, etc.) with no loss in sound quality.
It depends on how much money you're willing to throw at that car and what your actual goals are. I gutted my whole Nakamichi system in my '99 GS (basically the same as what you have in the LX), but kept the headunit/CD changer combo mainly due to aesthetics and keeping the installation simple (it was actually electrically more difficult, but mechanically easier). After ripping out all of the Nak speakers and amp, I am far from impressed with the quality, while the GS headunit is very well made and sounds excellent. The only complaint I've gotten is from some SQ show judges that did not like the fact that the Nak unit does not have a CD pause function, handy for testing system noise floor.
In your case, if you were to replace the headunit, I believe you would need a new CD changer as well, and then you have to think about its integration into the glove box (if that's where it is in the LX). I would definitely not worry about anything being sacred about the Nak system as long as you replace it with good components.