First, I bought my GL850s THROUGH LINSOUL, after speaking with Lillian about what was new that might be interesting, so no concerns about "vendor variation".
These are expensive headphones, so I will try to answer the questions that I would want to know the answers to before plunking-down this type of coin...
Are they worth it? To me, Yes! These are "specialty cans" that may also double as daily drivers if you've got nothing else. Why the specialty can classification? Because these headphones have an unusual tuning that is IDEAL for "LIVE" music. Orchestra, folksongs, acapella, and most "analog" sounds are rendered with incredible realism. An Andreas Eastman and a Stentor don't just "play the same notes", I can truly hear that they each have unique tone, resonance, and quality/amount of sustain/dampening. The GL850 makes instruments around like "music" and not just tone generators. I know I'm hearing "An Acoustic BASS", and not just BASS NOTES. I hear A CORONET", and not just BRASS NOTES interchangeable with a trumpet or flugelhorn.
The sound IS BIG, and there is so much going on in complex tracks that I can pick out, but not so much due to compression, (Bringing up the bottom at the cost of dynamic range) but because the instrument or voice separation sets them apart clearly. The stage is "decently-sized", but not huge with a long oval shape. Wide strong left and right with slight forward and definite rear space. Think of an oval and you're in the center when considering the lateral axis, but you're standing 3/4 of the way forward. You still have space in front of you, but most of it is clearly behind you. The GL850 IS NOT A BRIGHT HEADPHONE. I've seen comments all over the place about it, and I can't believe anyone would consider the GL850 bright, so I had to say that's "right out"! The GL850 is mellow and huge and comfy and warm like being smooshed by a huge and thick downy comforter of sound. It's odd because you would think that by this description that things are just a muffled, syrupy mess, but it's not. Detail is very good. Not the most detailed, but good. Clear - not "dry", not "thin", and not "edgy". Just present with no occlusion to any portion of its range detectable. You get everything.
My personal preference is for the perforated pads (As seen in the image above) and not the leather pads mine shipped with installed. I felt the perforated pads opened up the GL850, and made the cans sound less like 2 tower speakers pointed at your head on a 45 degree angle, while only 5-6 inches away from your temples. (The way they sounded to me with the default leather pads.)
Amping is fairly easy, and every dedicated amp I have was adequate to power the GL850. I did ultimately acquire a balanced cable, but it wasn't truly necessary. My favorite setup is DAC: Denafrips Pontus, and Amp: Denafrips Artemis. Though I also thoroughly enjoyed them on my Topping A90, Schiit Asgard 2, Cavalli LCX, and SMSL SP200, as well. Portable amps from my iFi xCAN up to my iCAN, iDSD Micro, and iDSD Micro Black Label all powered the GL850 quite capably as well. While I would avoid driving the GL850 direct from a cellphone, I imagine most reasonably current mainstream DAPs and dongle amps will do at least a passable job or better with the GL850.