I've said it before, headphones when out of the house are like glasses on your face, hat on your head, scarf, whatever - it's a head accessory. It has to at least lean a little bit towards looking decent with your general style.
In the house is entirely different. I walk around in pajamas and don't give two hoots how my hair or beard looks, so I wouldn't care how my headphones look either, but if I'm making this part of what I'm wearing out in the public, it has to have some semblance of your style in tact.
I think transplanting high quality drivers into Hello Kitty cans, though would be fun/ny, but the housing has a lot to do with the sound too ;) I don't think M-100 drivers would purr in the Hello Kitty housing haha. Who knows, it might be some miracle of an improvement. I still wouldn't wear them out of the house haha