I didn't much like the Stax amps, so I settled for the 323S til I could get a better one.
Following the BHSE thread and all the comments about delays, and since I find myself usually preferring a SS sound not tubes, I opted for the LLmk2
The lead time on the LLmk2 was also quite long(3 months?), and was extended a couple of times IIRC, but communication was very good at least in my case.
I also had some issues with the transformer on arrival, but the service was excellent, they gave me multiple options for how to fix it, and I got a replacement transformer within reasonable time.
Sadly I have not been able to get my hands on a BHSE or KGSSHV, so I can't give you a comparison between those SQ wise.
To my ears the LLmk2 is way better than the 323S in every way
(granted I liked the separate adjustment for left/right channels on the 323S, especially after seeing all those channel imbalance issues related to the SR-009).
However I still feel something is lacking in freqs 20-50Hz compared to the HD800, and I'm told this is not a fault in the SR-009 but rather the amping... Guess I might find out one day