I can't speak to in-ear headphones as I hate them. I own a few, but they were all cheap ones that I got for portability. I'm using a pair of Arctic Sound BT headphones and love them. They fold too so they are fairly portable. So I seldom need the in-ear ones I have.
The Xoom HD dock provides better sound quality than the built-in speakers, but its not going to please discerning listeners. If you're looking for high quality audio, get the standard dock and plug in a set of good powered speakers. I have no idea about 3rd party docks, but I wouldn't count on seeing any.
I recall seeing a cardock, but everytime the topic comes up, I can't help but think how much visibility or dash space would be eaten up by a tablet. Just seems like overkill unless it serves some business functionality.
I've seen a number of dates listed on sites for the Otterbox case. So its anyone's guess at this point. One date already passed. The next one I recall is like the 18th. But no dates listed from any major vendors, so I'm not holding my breath.
