Hello, I am one of the BAT VK-500 owners that you are likely referring to in your post.I bought mine second hand a couple years ago and had no problems with it until one of the channels pooped on it last year(8/99). After speaking with BAT's Victor K. about it, I decided to send the amp to them for repair and upgrades made to the VK-500 design since mine was manufactured. After an extremely long break in period(about 250+ hours playing time), the amp has really blossomed in my system(BAT VK-D5,VK-30,driving a pair of NHT 3.3's)and has been as steady as a rock since. I have no idea how the amp was treated prior to my ownership, but I know it was one of the earliest generation models. BAT was/is a pleasure to work with(spoke personally with Victor K. on many occasions)and they really stand behind their products big time! Highly recommended. Ken