I used to use Sennheiser PX100s, then discovered Koss PortaPros, and never looked back. PPs even have a Lifetime Guarantee, which means you return them, and they get a free repair, or replaced.
They sound amazing. Koss Porta Pro Stereo Headphones: Amazon.co.uk: Electronics
Have a look at the reviews; very bassy, lively, punchy sound. I was worried about them looking nerdy, but they're modest and actually quite attractive looking in reality, though the aesthetics may put some off.
Be wary of fakes on ebay, there are inferior Chinese copies of these, even though they're cheap.
All I need now is a decent headset button adapter (the wire on my Belkin wore away after a month)!
This review may be more convincing: http://www.goodcans.com/HeadphoneReviews/porta.htm