From what I've heard the 5800 is a dog. Stay away. Don't know about the 5802. Check the reviews. I would consider a Conrad Johnson amp to go with the preamp you already have. MF series is a good solid state choice. There are some available on the site. I have the MF-2200 and am very satisfied.
Advise sought on Adcom 5800/5802
I am considering getting an used Adcom 5800 or a used/new Adcom 5802. My preamp is a Conrad Johnson PV12 & my speakers are Eminent Technology LFT VIIIa (variation of a ribbon planar design). Timbral accuracy, lack of grain, tonal balance, realistic sounstage, tuneful bass with pitch definition more so than extension, are my main priorities. I listen mainly to classical music (covers the whole spectrum). Any advise will be much appreciated.