I was wondering what the impedance rating on headphones mean, do i want a lower or higher number? Or maybe do i want to match the impedance with the md player's? Gets me confused when i see these different ratings on headphones.

Ideally you get the most efficient power transfer matching impedence. Theoretically if you go to a slightly lower impedence you may get a little more volume at the risk of damaging the output stage. Higher impedence won't hurt, but you won't get the volume.
You're best bet is to stick with similar impedence, and try to get a more efficient headphone.
Good luck
Bob

* Moved to 'Phones section