Unfortunately I only had 3 nights with the amps before leaving on a 2 week vacation so these impressions as preliminary. Also, I only have an L700 so extrapolate what you will from this for a 009...
GG vs BHSE:
I have heard the BHSE but unfortunately it wasn’t through an L700 so I feel like it would an apples and oranges comparison. I heard the BHSE through the 009 which I didn’t care for at all but I find the same issue with the 009 through Stax amps too so I feel like it’s the headphones fault. I have also heard the Voce through the BHSE. The problems I have with that combination were at the opposite end of the spectrum with a very heavy emphasis on the lose frequencies and very little sound up top.
I’ll have more to share when I get back home in June. I’m also hoping to have some other e-stat enthusiasts over to compare other amp/headphone combinations in June.
Is it June yet?
I tried to read a lot of posts, and a lot of your posts, but didn't see that you got back to specifically comparing the KGGG and BHSE. I've been researching for too long, and buying a few things this year to try. Been to a lot of headphone meets; it's time to settle in on some type of end-game system. But not a T-2, yet. I've been trying the MySphere headphones and like them a lot, currently trying to make them comfortable on my head for long listening sessions (got them on my head now, not plugged in, with a little strategic experimental padding).
One conclusion I've reached: after hearing the MySpheres I can't go back to dynamic/planer designs.
Another: While the Raal ribbons might be great after the Jot-R is released, I'd want a tube-based preamp in the chain, or tube buffer, necessitating another power cord, interconnect, some more vibration isolation... I'm just not into that; I've got enough entanglement as it is!

One day when I get caught up with everything else, in 2025, I'll hang some rods/dowels from the ceiling, using cotton or silk thread, and get rid of the broken but quite strategically re-purposed clothes rack.
I originally decided against the SR-009 system because I was afraid (based on the experience of others) they would end up being too clinical.
However, now I've come to these two (or more) conclusions and would be glad to hear people's advice:
1) With either the BHSE or the KGGG, surely I can do a very minimal amount of tube rolling to suit my listening tastes. I've been into high-end audio for 40 years; I like well-produced music and don't care if I miss out on the last 5% of bass extension. I do want to be "involved", at the small expense of detail if absolutely necessary - hence my love of tubes.
2) While an electrostatic setup will preclude using its amplifier for other duties, that can be an advantage (no temptation to have a pair or two of planers and a pair or two of dynamics laying around for mood swings!).
3) Lastly, the idea of a T-2 in the future is appealing, if only for something to look forward to later. If I start wondering if the 009s with one of the two aforementioned amps is "sufficient" or if I would have been happier with something else (Raal or MySphere), there is no wondering if one is fortunate to be able to just order a T-2 instead, correct?
Comments will be appreciated; is there much between the BHSE or KGGG; are there any advantages of one over the other? If I find a real good used sample of either, by a good builder, just buy it and enjoy? Surely I can do some tube rolling to suit, while still not "ruining" the sound?