I have a pair of Elegia already that I run out of the iFi Go Blu (but also have tested with various dongles). Just about all of Apple’s Dolby Atmos stuff would be something considered mastered quiet. Since I’m listening with 256 AAC anyways, the hit from going BT isn’t bad at all IMO.
Thank you, I am going to post some info here as I am already testing it on my iFi Micro BL with what I BELIEVE is 18mw... This is based on numbers from a couple websites and me thinking my math and logic is good,
if I am wrong I would appreciate if anyone chime in. This is more for my benefit so I can preview things on my PC before getting the UTWS3, obviously these are approximations.
My amp is on "high sensitivity" and ECO mode.
Per the Amazon listing page, the voltage on eco mode is 2V output,
Eco mode- 2.0V/500 mW @ 8 Ohm (max), > 250 mW @ 16 Ohm (continuous)
this is coming from a ~0.5ohm resistance per Crinacle's website, in high sensitivity that is ~4 or ~8x meaning the watts @ 35 ohm(114.2857) is 1/8th,
https://crinacle.com/2019/02/02/ifi-micro-idsd-black-label-in-the-hands-of-a-non-believer/
13.285...mw @35ohm is approx the max power for the iFi iDSD Micro Black Label in Eco mode with high sensitivity on, which I have it on now
at full volume, it is again too loud, so with ~13mw or whatever this is outputting in relatively low power youtube is way more than ok
This reading makes sense to me since this is a good load for IEMs probably and that is what this combined mode is for....
Just from anecdotal evidence knowing it's made to drive IEMs safely it is already comparable to the UTWS3!
I cannot seem to find exactly what you are referring to, but I did notice many FLAC's I have seem to be much lower when playing them vs youtube's audio... likely because youtube's audio is mixed to be played over phone speakers as well
max volume is 5 o'clock
so with a few flac files and assuming around 13mw @ 35ohm max power, I prefer things slightly below what I would consider Average
Time - Pink Floyd - The Dark Side Of The Moon (HD Remastered) - 3-4o'clock is comfortable
Dua Lipa -Levitating - is just before 3o'clock, max hurts
Money - Pink Floyd - The Dark Side Of The Moon (HD Remastered) - Volume knob is maxed, I would enjoy maybe a bit more sometimes if I wanted to jam out, but it is OK I would say this is my average listening level, considering 2x power is +3db I think +3db would be "perfect"... obviously this assumes 13mw is fairly accurate!
US And Them - Pink Floyd - The Dark Side Of The Moon (HD Remastered) - even lower volume, due to the way the dynamics are though I would say this is about my average listening volume, but only having +3db might not be enough for someone including me to jam out too
Good Times Bad Times - Led Zeppelin (HD Remastered Deluxe Edition) - max volume is a little too high, average listening is between 2 and 3 o clock
Dazed and Confused - Led Zeppelin (HD Remastered Deluxe Edition) - max volume is a bit over my listening, on the fence if +3db is enough to jam but I think for most people it's just enough, again for me 2-3o'clock is normal
Anyway I would post more but I want someone to check my math, and regardless all these numbers are based on ~ ohm numbers...
I would say if my method is correct one can assume the power in this mode is between ~13-26mw which is more or less on the upper end the same as the UTWS3 since it is greater than/equal to 25mw....
I can see what you are saying where volume is indeed becoming a problem, if +3db is available I think it's fine and TBH would rank right along most other good volume level BT headphones sound volume anyway, if this is the upper limit it would still rank besides many BT headphones, just with the sets that are more average.... I however do NOT think it would be on the low/bad volume side, but it is indeed very close so I cannot say for sure without just trying the UTWS3.... I will post my finding with the same songs then and see how it stacks up but I hope this extra info I am posting well help others understand and make a good choice... if Fiio makes another unit with say something like 70mw + EQ and around $100 I think this would 100% be a slam dunk though, we are getting very close to making many good headphones able to simply be wireless with these adapters, and in the recent head-fi canjam youtube video I believe I saw the deva adapter is now able to be used with other Hifiman headphones which was the eventual progression as things got better vs just making the unit smaller/lighter!
EDIT- I have gone ahead and ordered all parts, I was able to get them 1 trip, and found reasonably priced adapters.... that said I added something in so total price is around $250, I will be posting something on this later, items arrive monday because I didn't want to pay $10 for next day shipping 
