I have them also, you might want to look to get some replacement ear pads
http://www.amazon.com/Beyerdynamic-Velour-Earcushions-MDR750...
http://www.amazon.com/Beyerdynamic-Velour-Earcushions-MDR750...
The earpads will go and start flaking (for me after 5 years). They are easy to replace though.
If you keep going down the audiophile rabbit hole like I did, next up is a DAC or a tube amp. A good starter cheap one (sub $100) is the Qinpu: