Just got the Ananda Stealth on literally Friday so too early to say but it might be that. Struggling some with the comfort but man it sounds good.
I was trying to avoid immediate comparisons but man switching from the 6XX to the Ananda is not flattering to the Sennheisers in terms of bass definition/extension and soundstage.
These are my first IEM purchases since high school! I got 3 or 4 which all died on me within a year (either the left or right side would lose basically all volume - I assume it was a cord issue but none of them had replaceable cords) and I gave up on them after that.
But now pretty much anything decent will have a detachable cord so . . . progress!
I got the Dawn Pro as well.
As for IEMs:
7hz Salnotes Zero
Tangzu Wan'er S.G. (I know the name's origin but I'm sorry - I see it and I think "wanker" and I'm not even British)
Dunu Titan S.
Not technically related since I bought them on AliExpress last week but also picked up the KZ ZST Pro X and the VE Monks.
It's hard to really talk about it without knowing what you're comparing against.
But I think the soundstage of the HD6XX is reasonable. "Intimate" is a word I'd use. I don't think it feels congested or small, but it isn't spacious either. I think it avoids the negative qualities I personally encounter on headphones or IEMs that have bad staging.
I think a lot of people really enjoy the 6XX for what it offers. But it's not soundstage focused, to be sure.