Question would be why? What are you looking for?
I made a couple questionable purchases before spending much time here. I'm content with my Alpha Dogs (balanced Cable), Oppo HA-1, and Uptone Regen (yellow) but I still question "what could have been". I feel an open headphone (likely a dynamic) should be my next purchase, something warmish to offset the HA-1/Sabre glare while also being a different flavor compared to the Alpha Dogs.
If you were considering the 660S, what about the 650?
I might just pick up a 6XX the way things are going.
Yeah, do that, and see what you think. Mods go a long way, believe me. But then having the right amp goes even further. Something like the Vali 2 or Massdrop CTH sound pretty good on the HD650, but pair them with something like a TOTL Eddie Current tube amp, and they scale beyond what you might think possible.
The AFO is a great headphone too, in my opinion. But I think the 6XX is a safer starting point if you're testing waters at this time. If after trying the 6XX, maybe modding it, and trying amps with it you still find something lacking, we can go from there. Maybe the AFO would be a good choice, or maybe something else. Or maybe it would make for a good complement with the 6XX.
I think the biggest thing is, if your goal is "something different" and you've got a MrSpeakers planar right now, a Sennheiser dynamic fits the goal better than a different MrSpeakers planar.
The 6XX is such a killer value.
Thanks for your comments. What I really need is a different flavour and a vali 2 and 6xx seem like the most logical choice.
Separate names with a comma.