UPDATE 1 (copied to the OP)

Amazon had the XS on for £393 ($474) with free same day delivery so I couldn't resist. I'm a firm believer in the burn-in theory, especially so with these as it is actually recommended, so they're going into a drawer with an old mobile phone playing a radio station for a few days before I make any judgements.

The BTR5 can drive them in SE, but only just. I can easily take the volume up to max and still listen comfortably so, given that the Qudelix is often mentioned in the same breath as the XS, I've ordered one and a 2.5mm balanced cable. Hopefully they'll arrive by the time the burn-in is done, then I'll let you know what I think.

So weird that they messed up the headband like that. Yeah, the BTR7 is too big. Had it offered something new and amazing it might have been worth it but no, that and the lack of clip puts me off. I've ordered a Qudelix as almost everyone says it's the best solution.

Yeah, I'm hoping to be able to stick with my BTR5 using its balanced output for the extra power and with that in mind and not wanting to have to swap cables too often, it seemed notable that the DX5 doesn't have it.

"... comparing 1kg of steel and 1kg of feathers" - That's OK, I live in a vacuum. lol. (https://www.youtube.com/watch?v=E43-CfukEgs)

TBH I'm not sure what's really driving me to want to try open-back, I'm certainly not dissatisfied with the Dusk in any way. I think it's that the reviews of the XS are just as glowing and impressed as the Dusk were - "This is the device to beat under $500" - so I want to try it, after all I like all kinds of music so why not all kinds of ways of listening to it.

Ideally I want an equivalent to the BTRx that works equally well on the desktop and mobile and with both devices, and definitely one with USB input (I only listen on my PC and phone) so the A50s wouldn't be suitable but any other suggestions would be welcome.

Thanks. With the Quedelix and BTR5 being roughly equivalent I keep thinking that if I'm going to spend money it should be on an actual upgrade such as the Topping DX5, which I like the look of but oddly it doesn't have balanced output!

Thanks for your thoughts, I keep reading that the XS is "Ananda with bass" like the Dusk is a B2D with bass so I'm hoping there will be similarities with the gentle amount of added bass to an already great device.

You won't get an argument from me. :)

That's what I'm afraid of, I can barely imagine anything sounding better!

Thanks for the long reply. Yes, that's what I'm thinking so far - $15 isn't much to be able to use it in balanced mode which, most seem to agree, will let them work happily with the BTR5.

I may upgrade to a BTR7 later to give me more power overhead and the ability to add the 2 EQ tweaks that several reviewers think is all that is needed to make them 'perfect' but that's the simplest solution.

Absolutely; as much as I am passionately in love with my Dawns, part of my reason for wanting to try open-back is that I do feel cut off wearing IEMs - I have no idea the wife wants me until I jump out of my skin when she taps me on the shoulder.

As the Dawn and XS aren't far off price-wise I would expect them to be equally good, just different, so I would be very interested in the thoughts of someone who has tried both but your experience is useful, thanks.

Thanks for the reply. Sure, they will definitely sound very different, I'm thinking more of how they compare on the 'hierarchy' ladder - a side-grade or definite upgrade.