Ayre MX-RPrice: $18,500 per pair

Website: www.ayre.com

Peter said: The MX-R monoblock amplifiers signified the dawning of a new era at Ayre. With their prodigious power capabilities, they can drive the difficult loads of low-sensitivity speakers with aplomb. Most important, however, they deliver the sonic goods, possessing that very rare ability to communicate in captivating fashion even the music on less-than-stellar recordings. That multiple tube fanatics of my acquaintance have ditched their tube power amps in favor of MX-Rs says it all.

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Read the Ultra Audio review.

The gist: Compact design, reference sound.