ARC REF75 biamped with a stereo ARC DS450. Sweet and thunderous!
http://www.stereophile.com/content/audio-research-reference-75-power-amplifier
Conclusions
The Reference 75 touched me on a deeply personal level. I enjoyed listening to music so much through it that every time I entered the listening room and saw its silvery hulk beckoning to me, I turned it on and played some music. More than with any other component I've reviewed, when the Ref 75 was in my system, I went out of my way to make sure, every chance I could, that music was playing.
I expect the Reference 75 will create some marketing problems for Audio Research. It has no flaws, and several strengths that exceed the performance of any amplifier I've heard in my home. And if it's true that amplifiers with a single pair of push-pull output tubes have a certain "magic" that can be lost when multiple pairs of tubes are ganged to create great power output, then I wonder how the sound of some of the higher-powered ARC amps will stand up to the Ref 75. And while the speakers I used with the Ref 75 were fairly efficient, I did play them at very loud levels in a very large room, and not once did I tax the amp's power-delivery capabilities. I would suspect that unless someone has very insensitive loudspeakers and/or a very large room, it would be difficult to make a case for why anyone would need an amplifier with more power than the Reference 75.
I wrote what was to have been this review's final paragraph some time ago:
"John Atkinson has said that there is no greater praise a reviewer can give a component than to purchase it for use in his own reference system. And although I loved my time with the Reference 75, and felt it equaled or exceeded the performance of my Reference 110 overall, I still love my Ref 110. With the decline of the financial-services industry in the recent meltdown, I'm earning a fraction of what I did 10 years ago, even as I have one child beginning college this year and another not far behind. I can't justify the luxury of purchasing a new stereo amplifier this year."
The hell with it. I'm buying the Audio Research Reference 75.