Yes HD600 is thin in the low bass. HD650 is better but to thick in the upper bass/lower mid. Overall I feel HD600 is the better mix-tool though.

Any decent amp will do and do not really change the bass.

Best IME is to use HD650 with a slight EQ to tame the 60Hz-350hz bump or so. I'm planning to build a two channel head-amp with built in notch for HD650 and bass gain for HD600.

Most people agree on these listening impressions and my measurements supports this as well.

Check graphs in post #12.

Nearfield monitor most similar to HD-650s?


/Peter