okay so I'm a real noob at this whole thing, I'm trying to understand why it would be better to have high impedence headphones? head-fi gurus, school me please.
okay so I'm a real noob at this whole thing, I'm trying to understand why it would be better to have high impedence headphones? head-fi gurus, school me please.
Their main advantage being they scale well with your (assuming) already robust and beefy high-end audio systems.
My fifth great grandfather could have schooled you, he was Georg Ohm! 
lol, I have the HD555 I'm thinking of replacing it with the BeyerDynamic DT880 but not sure which to go for the 250 or 600ohm. It will be used on a Xonar Essence STX, I know a dedicated amp would be better but maybe in the future. Will it be worth it to go for the 600ohm version or just go with the 250 ?
You can start with this thread:
http://www.head-fi.org/forum/thread/513393/guide-sonic-differences-between-dt770-dt990-models-more
This is a good post on headphone impedance.
The original reason to push to higher impedance was for studio work where multiple headphone connections were wired in (I want to say) parallel. Every time you add another pair of low-impedance headphone, you greatly increase the load on the amp. Higher impedance headphones demand a more predictable amount of power. I think it now has more to do with incidental design differences and synergy between your headphones and whatever amp you happen to be using.
so if I dont have a high end system or not planning on upgrading my system the 250ohm should be fine?
I wouldn't recommend any detailed headphones out of an internal soundcard. They do claim they can handle serious headphones, but I definitely wouldn't use the 600 ohms on that amp.
woah, awesome.