MAC fans - MC206 harsh?

I was just over a friends house. He has been complaining for some time that his Macintosh MC206 multichannel amp is harsh and bright. He Has B&W802N's and he is bi-amping each speaker using two channels of the MC206 per speaker (the other two channels do his matching center channel). Cable's and IC's are top to the line straightwire. Pre-amp is a Lexicon MC12(?). Sources are Pioneer CLD-95 laserdisc and Pionner DVD09 DVD player.

First of all, the CLD-95 sounds better then the DVD09 in analog. Now that we got that out of the way lets move on to the real problem. When he turns up the volume the system just looses it. I mean, the sound gets harsh and the music looses all the detail and nauce. Now, I don't mean 'piss of the neighbors' loud; I mean moderately loud but you can still talk over it with a little effort. At low volume levels, like background music, the system sounds pretty good (not actually my cup of tea...). We played around with placement of the speakers and room treatments, but nothing really helped.

So, any suggestions or insight?

PS-all listening done in two channel.