Ah, your explanation for headphones makes sense. If you're really into it, you should invest in a headphone amp and headphones meant to be driven by a dedicated amp. However, the value of this is questionable when you're plugging a souce that's already amplifying the signal somewhat into the dedicated headphone amp. It's still an improvement, but the relationship is complex and subjective. Any 'phones can be plugged into a headphone amp, but the better types meant to be driven by a dedicated amp have different electrical properties, mostly impedance.

Check www.headphone.com for an excellent and well-priced portable headphone amp, the HeadRoom Total AirHead ($99).

Ah, I thought of a solution that is actually getting me excited! I think the N810 would be able to drive the cousin of the AirHead called the BitHead, which is basically an outboard DAC (soundcard) too: that would clean up the audio quality greatly since the N810 would be supplying a perfect digital signal to the amp--as good as plugging an optical cable into your amp.

The only question is if the USB device would work, but I think the probability is high. Has anyone tested tested a USB soundcard with OS2008 and/or the N810 yet? If it doesn't work already, it should be feasible since it's a very simple and standard device. The Bithead takes batteries, so it shouldn't have any issues with a lack of USB power either.