So I recently bought a pair of Sennheiser HD558s and I was wondering where I should listen to music online. I usually go on Youtube, but earlier I was listening to a track I liked and it sounded kinda awful. Kinda like when a can of pop comes off sour or bitter.

So I busted my headphones, and have decided to upgrade. I've allocated $200 for the hunt on eBay. What should I get?   I'm looking for open, clear sound. I fell in love with the Sennheiser 800HDs the first time I heard them, but that's long out of my reach. I need something that can be...