Given your interest in the AKG, do look up the K-550 that streetdragon mentions.It's
a closed design but many people report it has a particularly good soundstage.
You might spend some time considering if you really want to move
to an open design, however.
Also do you think you're being limited by your RAZR HD? Have you
tried plugging in your M50s and K240s into another source to
see if they sound quite different (or the same) with a different
player & amp circuit?