Asheville does not fit all of your criteria, but it's a great small city surrounded by mountains, with a very hip downtown vibe, very unique and unlike the rest of the south.
Denver is a very nice city. I've never been to Austin, but heard good things.
If you want to live in New England, I'd check out some of the historic towns and small cities in and around NYC and Boston, though they will be very expensive, and it gets cold.
You might want to concentrate on college towns, as many of them are "walking" towns with a big city vibe, but without the minuses of big cities.
city-data.com is a good website to narrow your choices, but beware locals who hate outsiders and constantly post negative comments. If you go on the western states boards, don't mention you are from CA, as they won't have nice things to say to you. Many of them feel there are too many CA expats "invading" the rocky mountains.
Best places is also a good tool: http://www.bestplaces.net
Good luck with your relocation! :-)
“The only way to deal with an unfree world is to become so absolutely free that your very existence is an act of rebellion.”
― Albert Camus