I have heard the Topaz, although not with any Tannoy speakers, and it is a very good amp. The Kensington I heard were fairly easy to drive; they worked well with amps that were rated at 15 watts to about 50 watts that I heard coupled to the speaker. Based on what I heard with the Kensington, I would look for something with a that would not be excessively hard or brittle sounding at the higher end of the midrange. That means I would pay attention to how it works with solid state and some of the higher-powered tube gear that have a tendency to sound "hard" in the same range.
I have heard the MC275 on efficient speakers not too long ago and the particular setup sounded terrible--muddled and lifeless. A short while later I saw an episode of "How it is Made" that featured the construction of the amp, and frankly it was shocking. I would never buy anything built like this. All of the input connections and the connections to the speaker terminals are made by a press-fit printed circuit board, meaning that even the output to the speakers is being carried by a mere board traces, and no connections are soldered. The winding of the output transformers was done on a machine that appears to do four or five transformers in a matter of seconds--so much for the handwound, interleaved, and carefully insulated transformers that made McIntosh amps something special.
