I just made the same step you might possibly make...I was always a big car stereo buff & swore by Nakamichis old stuff such as the pa304 amp and many other Nak components that made up my system. In the car audio realm, Nak is one of the better ones out there, however, in home audio, I dont think they will quite have the sound you are looking for and are definitely not really high end IMHO. I got rid of my prized car stereo when I sold my car in 1995 and have missed the sound ever since. I built a couple systems since then and still couldnt match the sound...however, since you are moving from high end car audio to high end home like myself you may find what I am doing interesting. I first bought a pair of decent speakers. You can find plenty of great speakers that you have probably never heard of used for 500-1000. I then bought a used Bryston B-60 on a Dr's recommendation (he has 4 systems totalling over 250k) The amp was a little over 800 and let me tell you...I would trade this 2 channel sound with home theater (since I use it for music equally) for any Denon NAD Nakamichi etc etc. I originally demoed my B&W CDM1nt's with a Denon AVR5800. The 60 watt (mine specs at 70) BLOWS the Denon away...I know that I have only just entered the realm of high end audio and am pretty close to the bottom of the ladder but If you think that car audio can be addictive, wait till you have a taste of this candy.
Enjoy
Enjoy