The May + Bliss setting will sound better.
Most likely we will not hear a striking difference between Bliss and Niimbus. The choice of one or another amplifier will come down to the individual preferences of the listener and the composition of the headphones available. But the difference between May and Chord Qutest will be much more significant. I know that some HeadFi members have switched from Chord Dave to May and found May more melodious. Qutest is clearly not at their level, no matter how good it sounds.
Chord Qutest has only RCA outputs and the maximum voltage on them is 3 Volts.
All the DACs I've listened to with the Violectric 550 and Niimbus have always played better through the XLR. The more voltage they could apply to the amplifier, the more power reserve the amplifier had, the sound was more emotional.
May gives out 2.4 volts on RCA, 5.8 volts on XLR.
If your bank account and wife allow you, then it is better to choose May.
I haven't heard Expanse yet, but I've managed to listen to Stealth from Burson Soloist GT, Ferrum ORR+Gypsos, Violectric 550, Niimbus.
In combination with Stealth, I would put these boosters in the following order:
№1 Niimbus. It has a neutral setting, excellent stage, speed, bass punch, phenomenal resolution and a magical scattering of diamonds at high frequencies.
№2 Violectric 550. Everything is exactly the same as Niimbus, only the tuning is a little warmer and Niimbus has slightly better control of the headphone membrane (this is only audible at low frequencies and on single tracks). In all other respects they have parity (by ear).
№3 Burson Soloist GT. It has a lower speed (it's audible on fast bass compositions) and rounding of high frequencies (you won't hear a magical scattering of diamonds at high frequencies), less black background.
№4 Ferrum ORR + Gypsos. Smaller scene and resolution. The drop in resolution is strongly audible in the low-frequency range, it plays somehow simplified. This is the warmest of all four amplifiers. Gives an additional emphasis on the bass and rounds out the high frequencies (as you already understood, the sound without diamonds).
I gave an example of how Stealth sounds on these amplifiers. Given that Expanse has a similar magnetic system and membrane, it will react similarly to amplifiers.
If I had a choice now, would I buy May+ Bliss or May+Niimbus? My choice would be May+Bliss (even though I'm a Vio/Niimbus fan). Selling Bliss on the secondary market will be much easier, faster, with minimal loss of value if you don’t like its sound. This is due to the fact that the hype for Bliss continues to gain momentum. Everyone who bought it did not abandon it in favor of another amplifier.
Vio/Niimbus has never had the hype and is more expensive than the competition. Therefore, the discount when selling on the secondary market will always be greater. But those who have tried this equipment and understand its advantages are ready to pay the appointed amount.
Moreover, dealers in my area have sold a lot of Vio550/Vio590/Niimbus in the last 3-4 years. And I don't see them on the secondary market (in my region). That is, those who bought them see no reason to change them for something else. I also have no idea that I could change my Vio590 (I use it as an amplifier in my installation). My Vio590 (as an amplifier) outplayed all the amplifiers that I managed to own and hear (except Niimbus).