I'm looking for a nice pair of in-ear headphones for my iPod. Since a lot of what I listen to these days on the go are spoken-word podcasts, I'm not necessarily looking for the absolute best sound reproduction (as long as it's nothing too tinny). But I do want a pair that have a good seal with the ear canal for sound isolation, and are fairly hardy - my original iPod ear buds' rubber is falling off, and the left earphone on my Philips replacement set has gone kaput. Oh, and whose cord doesn't tangle too often! Anyone have experience with the Sennheiser CX300s or the Shure SE110s?