Sennheiser makes good headphones, I'm sure (haven't tried them myself), but if you're want stellar headphone on the cheap, get a pair of Grado Labs SR60s. (60-70 bucks)
http://www.gradolabs.com/
a review
http://www.goodcans.com/HeadphoneReviews/60vs80.htm
Honestly, I stole a pair from my dad 8 years ago and they STILL sound better than 99% of headphones on the market...by 'on the market' i mean the consumer headphones you can buy at Best Buy or Circuit City...places like that, where they only sell headphones that range in proce form 5 to 125 bucks and the most expensive pair at the store are the Bose Triport, which Trisuck!
Grado labs are handmade in brooklyn. Father and son establishment. All they make is headphone....just headphones.
The bass on these headphone is amazing. Truly unlike anything I've ever heard. The funny thing is, on an ipod, the SR60 sound better than the SR80s (the next model up) because the SR60s don't need a preamp. You can have the nicest headphones on earth, but you get any of the range from an ipod, because amazing headphone need a little power (preamp) to get the full range of sound.
They are open-air headphones, which means your ears and driver are not completely encased, which also means if you get on a elevator or go into a room with little to no noise, other people will be able to hear your headphone, and if you listen to Fantomas or Ennio Morricone* at high volume, you are guaranteed to get strange looks.
*Walking around downtown San Francisco listening to the score of A Fistful of Dollars at full volume is an amazing experience. Actually, just walking anywhere listening to a Fistful of Dollars is f&^king awesome. Ennio Morricone is the best composer ever.
EDIT: I also forgot to mentio that these headphone have a nice retro 70s look to them. I also edited the body a ton because I can't spell and I think too fast for my hands.