However... my close 2nd... and... maybe my first for the money... is the "ClassDAudio" SDS-470C at $700. Regulated linear power supply, so no "class d" sound issues. To me it sounds almost identical to the A21, and they have multi-channel amps also for very good prices. Much lighter, cooler and cheaper. I've had mine for 3+ years - it's been great!
http://www.classdaudio.com/sds-series-amplifiers/sds-470c-class-d-audio-power-amplifier/