After lots of research into headphones I think I finally found the right ones for my tastes:
After seriously considering the Ultrasone 650, 700 or DJ1, I found
Beyerdynamic 770s / 80 ohm version. They have powerful accurate bass, enough soundstage (giving a spacious feel to the sound), great build quality and they cost something like 150$
The bigger soundstage, bigger bass and better build quality are the reasons I chose them over the ultrasones. Although, from what I hear, the Ultrasones reproduce higher sounds better, are in general a bit more accurate and don't need so good amps to bring out the best in them.
I'm not saying that the 770s are better for everyone, I just think they suit my individual tastes better. And even this is just how I feel from the description others give. I need to try them myself to be sure.
Now I have to find a good external amp/soundcard combination for them that doesn't cost too much (I hear that the Bithead doesn't have enough juice to complement the beyers)! All the recommended amps seem to cost well over 300$ and all the cheap good soundcards aren't external. Now I need to do at least 2x more research! HORRORS!!!
It never ends!
BTW: I need to be VERY careful not to get into a vicious circle now that I joined head-fi. It seems even better than this forum for emptying your wallet
