I have a pair of
Sennheiser CX300s. They sound much better than any other earbuds I've tried in that price range. The bass response is simply unbvelievable. I had to plug them into my reciever and play the depth charge scene in U-571 just to hear the bass from the explosions.
They don't sacrifice the mid and high range for bass either. The highs are smooth and detailed without being the slightest bit harsh. Mids are clear and not muddy. They work great on planes too. I even use the headphones as earplugs sometimes and don't even plug them into a player. The phones come with three different sized fittings so you most likely wouldn't have a problem fitting them in your ears.