I think that I felt similarly too really and why I didn't go out of my way to find the Element III. Whilst the EF400 seems to have a more divided opinion, it is, to me a logical addition to the Zen Stack which I own. I do not tend to prefer to the more sterile and analytical sound of say the Topping or SMSL equipment, so I am very happy with my choice.

I think that they are a definite step up. The Sundaras are very neutral and I find that they can sound thin with certain songs. I don’t find them at all fatiguing though and can wear them all day. Most of my friends and family who have tried all my headphones would put these second to the LCD-X. The Audeze have far better imaging and layering in my opinion. Despite their weight, I find them very comfortable too and can wear them all evening. I do EQ them though. I have Sonarworks Sound ID Reference for headphones and the flat setting sounds amazing. I also have the Oratory1990 settings too. I alternate between genres and use either setting accordingly. I can’t imagine needing to upgrade these any time soon.

The Element III was running a dead heat with the HifiMan EF400 for me right up until I clicked the 'Confirm' button. The availability of the EF400 was ultimately the deciding factor. I have to say that I am loving the R2R DAC and am super happy with my purchase. Have to say though that it doesn't mean that the Element III will not end up in my collection at some point!
Hope you continue to enjoy it and it brings years of pleasure.

Flair has the list, but LCD-X are the first ones where I feel that there is nowhere left to go. Paired with the HifiMan EF400 is just perfect for my ears.