I've also heard the HD650 with my share of amps. One of the best combos was with the Gilmore Lite. It opened up the treble a bit and tightened up the bass. It didn't get rid of the mid bass hump but did the best it could with what the HD650 has to offer.
I've always been an advocate of having a properly balanced rig. It will give the best performance within your budget. The system is truly only as good as it's weakest link.
Edited by baka1969 - 10/26/11 at 5:41am