“In The Ghetto” Elvis Presley
“Pusherman” Curtis Mayfield.
“Bubbles” Yosi Horikawa.
“Aji” Steely Dan.
Plenty more but a few to add to the list. “Bubbles” is just fun a definite headphone test track.
Picked a pretty good pair to start your journey.

I agree with you the Spark does have a bit of warmth to it so might seem to bring out the bass a bit more maybe not for sure. I have a couple of other amps comparable in power and price ( JDS Labs Atom and Schiit Magni 3 ) and while I think they both sound pretty similar the Spark definitely sounds warmer. I’ve always liked the Spark as I was on the pre sale list for the original which was to be a portable amp .

This might hurt a warranty claim if you try to fix them yourself.
At CanJam Chicago last year was listening to a pair of LCD-5’s ( not at the Audeze booth ) and when I took them off the right side connector just fell out on it’s own but the wires stayed connected as I wasn’t changing cables just taking them off. Hope you get it fixed.

Excellent first setup. The Schiit stack is a solid combo and the 6XX’s are still a bargain I got a pair on the first run from Massdrop I think in 2016 but took awhile before they arrived but worth the wait just a very good headphone.
If you really want to hear those vocals a Bottlehead Crack + 6XX’s is just a awesome pairing .

They are expensive as well $269.

I commented on that thread and as others said probably not being driven well enough , as what you were hearing was definitely not what I’m hearing from my Diana TC’s.
I’m glad you didn’t give up on them as I listen to them much more than the other headphones I have and with the new bass ported pads gives them some added bass punch and also widens the soundstage a bit. I have not heard the Omega Lupi and 250 mW does seem a bit low but my Amps and Sound Kenzie only does 350 mW @ 32 ohms and the TC’s do sound fantastic with it as well. A lot of my listening is done thru my iFi iDSD Diablo as I like to sit out on the back patio with a brew or a bourbon or two when the weather is not too inhospitable.

For me if only one headphone it would be the Diana TC with the bass ported pads.

When you say they are quieter then you do not have a amp that will run them fully. Just some specs I saw for the Meridian Prime said 250mW @ 42 ohms so no not enough for the Diana TC’s.
My HiBy R6 Pro just gets them going on the low end of power and it puts out 750 mW at 32 ohms .

I just wonder why no electrostatic headphones on the list? Is it you haven’t heard any?
I will agree on your first 2 excellent headphones but the 660S’s I just don’t care for much. Really like the the Clears as well and only heard the 1990’s once and didn’t dislike them as I remember. Have the 6XX’s and Sundara’s and would also put them close together as they do what they do very well and at a good price. The LCD-2 closed backs I didn’t care for much but think the LCD-X is pretty good and would place them around the Arya’s as the first time I heard them I really liked them but after hearing them again still liked them but there was something that just seamed a bit off but could have been me and listening to too many headphone’s that day.
I will say I do agree with many of your impressions on many of these and I own 30+ headphones and have heard many many more. Just my subjective opinion. And to your oops the new Utopia in my opinion better than the original also a excellent headphone.

I have tried both but sorry not together. I’ve always liked LTA and came close to buying a Microzotl 2 but found a great price on a pair of Abyss AB-1266’s and was pretty sure it wouldn’t be a good fit but pretty sure the Z10E would do just fine. I think the only Estats I’ve heard from it are the DCA Voce and Stax SR-009’s and it was quite good but don’t think it is the best I’ve heard as the Woo 3ES is pretty special but didn’t hear them side by side . The CRBN from the 3ES is very good but the Stax SR-X9000 from the 3ES was amazing. I would also say the 3ES and CRBN was a bit better to me than the CRBN’s from a Blue Hawaii but that is just me.

And I guess you are the science?

So you have heard the Super Conductor cable ?

I’m hoping they have the closed backs at CanJam NYC in a little over a month.

Might have to check that out.

Abyss has used magnets to secure their pads for the AB-1266 OG’s in about 2013 or so not for sure of the time frame but close to ten years now. So it is not like people have not had a chance to replicate them.
The thing is there are a lot more HD-650’s and Sundara’s out there than Abyss Diana’s and you can find pads for them easily and they both use very different mountings to secure them . Pretty hard to adapt those to the Diana’s and vise versa.
While you think $260 is crazy for pads I get it but to mod something for a very unique headphone like these the time and labor would be so much more.
You might believe that they designed them so no one else can make easy to replicate ones.
They pop off and on in seconds why doesn’t everyone do it this way ?

Sorry but it is “ New Abyss Diana Bass Ported Pads” .

So all headphones should be made the same shape and size? So you can use any pads with them ? So no room in your world for advancement it shall be all the same.

Well they are $4500 headphone’s and the pads attach magnetically so you can’t just throw on some Brainwavz on them . The porting is in the base of the pad as the originals are flat so not easy to do. I have seen some using some spacers to lift the pads up a bit to maybe give the same effect but these work always without worry so I’m good.
What would be a acceptable price for you for a specifically designed pad that yes only works with one headphone?

So just got these a few days ago and have to say as advertised. They definitely boost the bass it is not crazy amounts but it is very noticeable and also the added benefit of a bit more soundstage to them as well. Going back and forth between pads and still do not hear anything that has been lost on the pad change. Yes they are expensive as I paid $260 for them but I am not regretting it in the least . It is a upgrade .

I have a few of some would call “Summit Fi” and most of them are Open Backs and still some closed backs and IEM’s sound very good as well but would still go with a open back myself.

I think you can look at all the graphs you want but I do not think they will tell how they sound by the graph. What I mean is Grado sound like Grado’s and Sennheiser sounds like a Sennheiser’s and not sure a graph can tell you which other than knowing the the headphone specific response could you tell I don’t think it accounts for tone.

While I have not tried a Magni with the HE-6seV2 I’m pretty sure it needs more . Even with my Master 9 it is good but probably could handle a bit more.

My iPad Pro is newer so no headphone jack but do have an older iPad with a headphone jack and it does a pretty good job driving my HD-6XX’s which are pretty much HD-650 but the 600’s are a bit less sensitive so probably not going to do as well so I would opt for a amp myself. Even hooking up a old Dragonfly Red I have was definitely much better sounding than the iPad alone.

Because the OP thought it should have came with a 4.4mm balanced cable from Sennheiser.

Not that comes from Sennheiser.