That's interesting about the TSC2301, but every portable device I've seen that's able to provide both an amplified signal an a line-out (the iPod and many other DAP's) have seperate outputs, so it could be that the N810 simply isn't set up for it. Without a crazy proprietary connector that somehow packs in 5 or more contacts onto a 1/8" (something like the stupid iPhone jack, but worse), I think that the only way to provide line-out in addition to an amped signal is with a seperate jack. I don't know if I read your post carefully, but if you suggested some kind of switch mechanism that would let the output switch between amped and line--well, that would be awesome.

About the Bithead, it really shouldn't need proprietary drivers on any modern system. It's just an outboard DAC (digital-to-analogue converter), which is one of the most simple and standard kinds of chips out there. It doesn't need a signal sent to it in any special way; it just receives the audio stream digitally over USB and the DAC converts it to an analogue signal. Done.

This is what the somewhat vague description on the site says:

I just learned about the choice it gives you of using USB power or running of battery power for a cleaner signal. Great! It also happens to solve the problem that the N810 would probably not supply enough power.

It's an efficient amp, too. They claim 30-35hrs of 4 AAA's.