I'd like to know this as well.
I have purchased and owned three Wells Audio Headphone Amplifiers. 1) Headtrip II, 2) Dragon LIII, and 3) Headtrip II LII. They each have their own character and strengths.
My first Wells Audio headphone amplifier purchase was a Headtrip II. I used it only with 1266TC and Arya V1s. I really enjoyed this amp. There was a bit of noise when adjusting the volume on this amp, but it was only present when turning the knob. Note that I had no noise when driving the Aryas with this amp. This is a powerful and dynamic sounding amp. I ended up getting lured into the Dragon after several listening sessions at Jeff's. I also wanted to dabble with some tube rolling so the Dragon seemed like a logical next step. I am space constrained and can have only one amp at a time. So I sold the Headtrip II and move over to the Dragon.
Enter the Dragon LIII. I had listened to this unit at Jeff's location when it had 100 hours on it. I believe that it was one of the first Dragon units he built. Then I listened to it again when it had about 400 hours on it. I finally purchased it after it had about 650 hours on it. The difference between these sessions was crazy. I think that the parts he is using take quite a while to burn in. This was enough to convince me that burn in is real. This amp has a wonderful airiness about it. It is 3 dimensional. I felt like I was sitting with the musicians. With the different gain settings, this amp scales amazingly well with headphones that have differing sensitivity and efficiency. It paired with and drove the 1266s quite well. The optical volume control is sensitive. The knob is heavy, but because it is optical, it doesn't have much resistance when turning.
I really loved the 3D sound from the Dragon LIII, but I missed the dynamics and speed of the Headtrip. I decided to upgrade from the Dragon LIII to a Headtrip II LII. I prefer the sound of the Headtrip II LII to the sound of the Dragon LIII. While I can't play with tubes and I can't adjust the gain settings. The Headtrip has better speed and power, though I don't get the same 3 dimensionality in my listening sessions. This amp now has about 850 hours on it and again it has opened up tremendously since the first 100 hours. I have added a pair of Susvaras to the stable. The Dragon LIII was capable of driving them, but they seem to bloom more so with the Headtrip II LII. I hear more detail in the mid range while maintaining a very natural sound. The Headtrip II LII is an endgame amp for me and I am still thrilled each time I listen to it. My unit has a Goldpoint attenuator which has a wonderful feel and resistance to it. It is also dead silent. I very much prefer this attenuator to the Khozmo on my first HT and to the optical attenuator on the Dragon LIII.
A few other thoughts....
Balancing the system - I've figured out that I really like sound of tube DACs. I have a Hugo2 that I use, mostly for portable/mobile listening. I actually prefer the sound of the Dragon with the Hugo2 when compared to the Headtrip with the Hugo2. The Dragon sounds awesome with my Cipher (much better than the Hugo2), but the Headtrip, to me, sounds even better. I suspect that the tube output stage on the Dragon helps with what I would describe as a more analytical nature of the Hugo2. I guess that it is tough to say which is better without taking into account the overall system.
Bang-for-the-buck - at nearly 3x the price, it doesn't seem super fair to compare the Headtrip II LII to the Dragon LIII. I do like the sound of the Headtrip II LII better than the Dragon LIII for the reasons mentioned above. However, at $5,500, the Dragon LIII is really tough to beat. A more fair comparison might be the Headtrip II to the Dragon LIII. My Headtrip II had an internal power supply and the Khozmo attenuator. My Headtrip II LII has an external power supply and a Goldpoint attenuator. Both of these I feel were substantial upgrades and contribute to my enjoyment of the upgraded Headtrip.
Hopefully my experience and these thoughts are useful...