Hello @SenyorC, I know I am replying to an old review of yours, but I thought I would like to take the opportunity to post an agreement.
As many of you know, I have been doing some upgrades. I recently bought the Sabaj a20d DAC/AMP So that I would have something to use when I am in State College. This device is fully balanced, quite modern, and adequately powered. I also bought a selection of Hart audio cables, including a cable with Sennheiser plugs. Now for the first time in a long time I am able to listen to the HD 6XX in a balanced mode.
On the Sabaj, listening to Santana’s Blessings and Miracles album on Qobuz at 96/24 I think I can fully appreciate the 6xx scalability. There is bass slam. The Sennheiser veil is gone although I would like a touch more shimmer on the cymbals.
The tracks I use for testing are “A Lighter Shade of Pale” and “Break” which follows. For comparison, I immediately played the same tracks with the Rosson RAD-0 Headphones. Are the Rossons better? Yes certainly, they should be at 10 times the price. Are they 10 times better? No way. They’re probably two times as good. (My own very subjective opinion, take that ASR)
This makes me yet more convinced that the 6xx/650 is a strong recommendation for newer users and one that will help them understand scalability and also provide a well understood audio yardstick.