Just wondering why Sony did not include their "HD digital amp" (from the Hi-MD walkmans) in any of their DAPs? I'm listening to my MZ-NH1 and it sounds, in some ways, better than my NWZ-A815. Hi-SP vs. 320kbps. Optical recording for the NH1 from my Sound Blaster X-Fi XtremeGamer sound card (no EQ'ing or other sound enhancements). No sound enhancements on my A815 either. I'm listening through my Senn PX100.