In what sense is the Marantz superior? They're very different actually and wouldn't be used in the same scenario. Harman is a stereo amp/receiver and the Marantz is an AVR.
That said, while the Marantz is extremely nice, as far as sound quality and components go the Harman Kardon HK990 is vastly superior. Not even in the same league internal build wise.
Marantz makes nice stereo amps as well, but this is an AVR and companies always make stereo equipment with higher end equipment then they put in to audio video receivers.
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