I can try and help:
Utopia:
Pros:
- Reeks of competence. It is my choice of reference headphone right now. I love a nice balanced sound, and this has a fantastic balance between the treble, mids, and highs.
- Very comfortable. More so than the Abyss, similar to the HEK (might be more or less, depends on the person. For me I might go with the Utopia)
- This is the first time I am bringing up looks for this list. The Utopia is sexy. I would easily put it above the HEK and Abyss in terms of looks, and personally think it looks better than the LCD-4. Don't get me wrong, the LCD-4 looks crazy good, but the Utopia has sex appeal. Can be compared to Arnold S. vs Ryan G. for example. One looks mean, one looks like you want to put it on (don't let my fiance read this, haha!)
Cons:
- This is the hottest headphone I have ever owned. Luckily I keep my room cold otherwise it might be an issue.
Abyss:
Pros:
- You haven't heard headphone sub bass until the Abyss.
- It can be so many different headphones with how adjustable it is. Forgiving to poor recordings.
- There's something about the imaging/soundstage. I found the soundstage to be more realistic than the HD 800, but still similarly wide. It has a very 3D effect. Now, the Utopia does this very well, too, but I think the Abyss's soundstage gives it an edge in that effect. It's surreal for a headphone.
Cons:
- To say THE LEAST, the weight and design are both abyssmal, haha... I love bad puns.
HEK v1/(somewhat v2)
Pros:
- Relaxed headphone -- for many, good for listening in the background while doing other stuff.
- Very comfortable -- I would dare to call it the same/better as a Utopia and for sure better than the Abyss/LCD-4.
- I thought it was well versed in classical and complex music. Great bass, great treble sparkle.
Cons:
- For me this list includes the laid back tone of the headphone. Never engaged me quite right and didn't stand a chance against the LCD-4 for my taste.
- Build quality made me laugh when I first opened it up. Surprised it didn't break during any shipping -- oh wait, the hard case fixed that I suppose. Surprised I never broke it during general use. This is a trade off though, considering the weight.
For the hell of it,
LCD-4:
Pros:
- It has the bass presence that can be compared to the HEK, but more accurate/better. I love Audeze's bass.
- The headphone looks good, and feels good for how damn heavy it is. I can sure feel it if I move and when I take it off, but the new headband is great.
- The mids are to die for, but I don't know if I would quite call it realistic. It is like the LCD-3 in a sense met with the LCD-X and had a better baby. (I gave up both of those phones for the LCD-4 originally)
Cons:
- Weight could be better, but it is what it is just like the Abyss. I buy headphones for the sound.
My speed ratings with my gear: Utopia > Abyss (<-very close->) LCD-4 > HEK v1/v2
Your choice to disagree, this is using my gear of course. The Utopia sounds faster than the Abyss and LCD-4 to me. The HEK was never a fast headphone for me.
Reference ratings: Utopia > LCD-4 > Abyss > HEK v1/v2
Some people may disagree with my reference ratings, but the LCD-4 got marked for treble and bass, Abyss got marked for treble sparkle and soundstage, and well the HEK never felt like a reference to me.
I have owned everything in this list, and can safely say I sold everything except the Abyss and Utopia.
For reference this is using custom silver cables from Ted Allen for all of these headphones. (the stock cables didn't make too much of a difference in comparison, but I have tried each headphone listed with multiple types of cables, both silver and copper)
I have custom power cables, USB cables, etc. etc.
I use a Simaudio Moon Neo 430HA with optional DAC and a Schiit Wyrd with two Audioquest Jitterbugs.
Currently have a Yggdrasil on the way to replace the 430's DAC portion as well -- hoping to eventually have impressions. Don't expect to have it for a couple weeks though.
I've owned the Utopia for around 2-4 weeks at this point.
I previously owned the HEK for 1-2 months and LCD-4 for 1-2 months.
I've owned my Abyss for about 9 months making it my longest owned flagship.
Let me know if I can write more details/thoughts for you. I have the time at the moment.