Would Totem Arro's be a significant upgrade from Kef Q150's

As commented by others, and having owned multiple Totem speakers, the amplifier used to drive the mains is key to get the most out of them. Your room shape is interesting, and with the Yamaha A-S501 you could try it, see how it goes and with your room shape. Streaming Spotify Premium also leaves some missing top-end and air [imo] which may bring a little more bottom end as a result.

If you try this, let’s say If you are not getting the low-end weight you want from the sound [and you don’t go for a higher current amp than what you have now] - another option might be to add a Totem Kin Sub later on as an alternative approach to bring in the bottom end re-enforcement. Fwiw, I tried 50w, 100w, 150w, 200wpc amps with my former Totem Model One Signature speakers, and once a higher current and higher quality dual mono SS amp was in place did I get the real bottom end out of my Totems. Not as good with my weighty 100wpc tube amp at the time, needed the 200wpc 75amp SS amp to make the Totem’s sing their best. This is why I mentioned the Totem Kin Sub as a sideways option too. Best of Luck.

If you can afford to beef up the amp I would do it!  Totem is one of the best ...

Check out Odyssey, Klaus builds tanks for amps and sound sweet.  More than enough moxy to make the Totems bloom.  20 year transferrable warranty.  Not a shill but a believer; I own his Kismet amp!!

https://odysseyaudio.com/#

I was reading some Totem Arros reviews and listings myself, as I was starting to second guess my recent purchase of a couple of Revel M126be’s. As far as recommended power, I guess Totem was saying 20 to 80 wpc (which made me think that they must be not a hard load to drive), however they are also listed as a 4 ohm load with sensitivity listed as 87 dB. Which doesn’t sound as if it would be a real easy load. So I posted a thread here on A’gon inquiring about those numbers, and someone replied that the numbers did not suggest a real easy load, but that they did suggest woofers that could not handle a lot of power.

Which I do not completely understand.

What appealed to me about them is that the reviews I read all seemed to say that they were not incredibly finicky about room size or placement and that detail and sound stage were great. The ’but’ was that they were incapable of "slam" with no real bass. Neither of which are super high on my list, but I am still waffling.

@immatthewj I don't think you love the Revels. By this time you should be happy with them - if they had your name on it. Are you considering to switch them, find a better fit?

@grislybutter , to begin with I thought I liked them, but now I am kind of feeling they may have actually been a lateral move.  Not that I don't think they sound good, just that maybe what I really wanted ("tell me what you want, what you really really want") was different.  Horns maybe, or maybe the concentric driver thing.  Second guessing myself has always been a curse for me.