I had a chance to try the Arya the other day. (And the Susvara at the same time.) I used to own the HEXV2 which I liked quite a lot, but eventually sold it because I preferred Audeze bass. HiFiMan's major selling point is the unmatched spaciousness. HiFiMan sounds like an open air concert, sound is everywhere. Bass is everywhere. First it impressed me too, but then I started to miss that bass punch and focus so I sold my HEXV2 and stuck with the awesome bass of my Audeze headphones even though the HEXV2 sounded more spacious and more natural in the upper frequencies. (I do like bassy music.)
The Arya to me sounds like a more resolving HEXV2. It is much warmer and much softer than I expected. A very comfortable and pleasantly spacious sound. I can see why so many people love this sound. It is also very good value for money if you look at those crazy priced flagships. The Arya is a very good mid-fi headphone if you like a relaxed and comfortable, slightly warm sound. Doesn't quite deliver the resolution of TOTL alternatives, but if you like HiFiMan sound and you don't have thousands to spend Arya is a very good option.
I personally still prefer a bit more punch and excitement with my electronic music (Audeze), even though it comes with a smaller soundstage. I am happy to sacrifice spaciousness for a more focused and more impactful sound/bass. But that is just my personal preference.
A few words about the Susvara. Yes, they are incredible headphones. Absolutely top league. Tuning is a bit different to any other HiFiMan headphones. Even to the HE1000V2. HE1000V2 can be a bit thin and treble heavy, the Susvara is nothing like that. Susvara sound combines the best of all HiFiMan line up. The detail and technical finesse of the HE1000V2, HE1000SE combined with the pleasant warmth of the Arya and HEXV2. A true masterpiece. But for 5-6K?
The Susvara is definitely not 6K good compared to the Arya or HE1000SE. That price is ludicrous.
Yes, the Susvara does play in the TOTL league, but IMO it is not the best value in the TOTL league. The Empyrean for less than 3K(!) offers a vastly superior design and build quality. If I didn't know anything about audio, I would guess the Empyrean is 6K and the Susvara is 3K based on build. The Susvara definitely didn't feel like 6K in my hands.
The LCD4 still has better bass than both. What the Susvara does best regardless of price is a very spacious, clean, detailed but still somewhat sweet and slightly warmish sound to a very, very high standard. Is the Susvara worth its price? No. But which TOTL headphone is? When you leave the 2K mark it is not about sensible decisions anymore. Taste comes first, money is secondary.