OK, my trusty Sony MDR 7509's (the old ones) are falling apart and I'm looking to replace them.

I AM getting a pair of ATH-M50's but also want a higher end (mid level ?) Sony or Sennheiser. I'm looking at the Sennheiser HD 600 or the Sony MDR-7520

Does anyone here have / use either, both ? Primary application is for mixing, not tracking, so I can go open or closed design.

NOT looking for alternative suggestions... there would be tons of opinions. Just hoping some guys here have the Senns' or the Sonys.