Okay, as crazy as it might sound i think i'm hearing a difference between having the case on/off. It's taken me a bit of AB testing to narrow down the differences.
No case: Very clean background, clear and expansive sound. Most analytical. (actually sounds closer to the sp1000 from memory which i demo'd without case).
Stock case: Adds some fullness particularly noticeable as i'm listening to Halie Lorens voice right now, but less expansion and clarity. Slightly closer, more intimate, fuller and smoother sound. Adds to the sense of timbre/musicality
Dignis case: Everything sounds bit bloated and dampened. Not as clean and analytical as caseless.
Now this is curious because i had demo'd the sp1000 without a case and the sp2000 with stock case on. The most noticeable difference i heard between them, analytical vs fuller more organic sound i found to be the changes above. When most reviewers have been reporting minor differences I've been a bit baffled about why i heard a more substantial difference but maybe now i know.
Stock case is my favorite sound, maybe i will try to find another semi open case and just keep the dignis on when travelling.
Btw i'll second aaf evo in saying that when i had the 100ii and even now i've never heard sound changed with AK updates.