@bclower: It's a little off topic, but would you mind sharing what made you prefer the DP-550 to the DP560? I have a sneaky suspicion that the newer Accuphase players and dacs (and maybe amplifiers as well) are not necessary better in all respects compared to their older machines.
As for your initial complain I'd like to add another fresh argument against blaming your wonderful amplification equipment for sins of frequency rolloff. I have just bought a pair of Sonus Faber Amati Futura. With my comparatively more modest electronics (Innuos Zen MK3, Accuphase DP550 and the E470 integrated) the sound has excellent extension both ways, in spite of the allegedly more restrained top octave of the Futura. Matching cables and the room do play a huge role! Even things you could dismiss as mere fine adjustments like the surface your gear sits on can be very important: I placed the speakers on the carpet first and the bass was a disaster; now they are on the wooden floor (in the same position) and there is a world of difference. FWIW