This is a better version of HD650, while also being cheaper. Same drivers, same sound, shorter cable with smaller jack - appropriate for modern portable amps, and the color doesn't chip away like the metallic grey on the HD650. Although, the dark blue was an odd choice, in my opinion. Very comfy. Regarding sound, I think it's a question of preference. I tried several headphones (AKG K702, several Beyerdynamics, Sennheiser HD600, HD700, HD 800s, Hifiman HE400i, some top-end Sony, some Audeze, several Audio Technica, one Grado) before deciding that I like HD650 best of all, so HD6XX was the best deal ever for me. It's just that I like mellow highs, less brightness, better control on the voice, tight bass but not overwhelming, they were just perfect. The only headphones on the shelf that I found to share the HD650 sound signature, while being slightly better (around 10 %) in every aspect (sound, looks, comfort) were the planar magnetic Oppo PM-1, but we're talking about 199$ vs. 1099$ and that says it all about the exceptional quality of Sennheiser HD6XX.