I'm using 2 of the good doctor's amp heads. I have a recent 6545, which is the channel switcher. Very cool amp, but a bit finicky. It doesn't like to sit on top of a cab (makes things go a little haywire/microphonic). This makes it hard to play on stage - I now sit it on its road case next to the cab...seems to work. Aside from that complaint, the amp is killer and sounds great.
I also have an older, 1993 SRZ-65RH, which is a big-box head with reverb. Made back when doc was building these alone in his house. In 1994, Joe Walsh took one of these out for the Hell Freezes Over tour, and the rest is history. This amp is a monster! I just wrestled our producer into giving it back to me - he had it in his recording studio and did not want to let it go. Killer clean tone and sweet, understated reverb. Crank the gain, and you have a nasty hot rock machine. The absolute key to this amp is to get a cool NOS 12AX7 in V1. Recommend Brimar or RFT. Both have done wonders for my amps!