My Mark IV. I may mess around and such with my other amps and preamps, but whenever I crank it up and play through it, it always feels like I am back home again. My other amps and such may be good, but the Mark IV is in a totally different league for me.
Bogner XTC Classic
Pretty good cleans
Blue channel is fantastic
Red channel is great at high gain heavy tones but just as important it can do some very very nice low gain, smooth blues tones with the gain set low and the Master turned up.
Extremely underrated amplifier