This has been upgraded two times by Steve McCormack at a cost of $3790, ( see attached photos of invoices for the mods ). Mods were done in 2012 and 2015. I'm selling off my system due to loss of hearing, I can't justify the investment anymore. It is a very fine amp and Steve is a pleasure to work with. I used the amp with a passive preamp driving Maggies for a wonderful presentation. I've owned many amps over the years and always came back to McCormack. I will sell to members with a history of positive feedback and verified PayPal address, lower 48 only. I'll split the shipping and insurance. Thanks for looking!