The 7550HD was a great product, powerful high-current amplifiers, (2) TI DA710 DSPs, had Logic 7 which
could overlay Dolby True Audio & DTS HD delivering an incredible 7.1 soundstage. I still have a 7550HD in 1 of my HT systems, that has been running fine for >10 years. What many may not know is that the HK AVR development team
also designed AVRs for multiple Onkyo platforms including the 605/805...
Just my $0.02...