Hi wizard, I recognize many of those models. during the early days of Boulder, ironically enough, they were once local to me based in Encinitas California a beach community a few miles so. of the mod squad. their claim to fame back then (still is?) were discrete op amps used for everything up to the output stages. they wrote a paper dispelling the superiority of those little "fire bottles." At the time I was considering a boulder but was so put off by his stance against tubes I bought an ARC Sp-8 preamp instead.