Originally Posted by glober
A friend of mine recommended Beyerdynamic DT 770 PRO-250 (these require a headphone amp right)?
No, you don't need a separate amplifier - they'll work on any normal headphone output. On low impedance outputs, like an mp3 player or a smart-phone, you'll just not get the full sound potential out of them.
Headphone output impedance is usually listed in the "technical specifications" section of the manual for your mixer or soundcard - or whatever you're using.
One thing about Beyerdynamic phones is that their design doesn't fit everyone. I personally have a relatively big balloon shaped head and can't wear them for very long before it becomes painful (and distracting). They also tend to be very warm, so if you're a sweaty lard-ass like myself, open designs like the ones from Grado Labs are worth checking out as well.
In any case, if you order your headphones online wihtout having tried them on first, it's a good idea to be very critical about how well they fit you, - not only about how good they sound.