Thought I would add some observations/experiences on this category of mini-amps with separate "power brick" power supplies.
Have you seen any reviews with actual test data on these miniature amplifiers?
As small as they are, and without vents for cooling, they certainly defy normal conventions!
None of the ones I looked at provided FTC/RMS power specifications, but reviews made it clear that they were capable of powering typical speakers reasonably well.
Also, NoAudiophile.com is recommending the $65 SMSL SA-50 as the amplifier in his recommended systems that use passive speakers. Although he provides no review of the amp, he has mentioned using it some of his reviews, and he does provide good testing/analysis of the speakers he reviews, so I take his recommendation a bit more serious than "just another YouTube review".
Looking for a flexible alternative to a soundbar, and wanting remote control, sub output, as well as optical, analog, and BT inputs, I settled on an SMSL AD-18 for $145.
https://www.amazon.com/SMSL-AD18-Amplifier-Bluetooth-Subwoofer/dp/B071JN7GXN/ref=sr_1_1?s=electronics&ie=UTF8&qid=1523292189&sr=1-1&keywords=smsl+ad-18
I have not yet attempted to compare the amp to others while listening critically, but nothing has impressed me as "off" when listening to Energy RC-10's on it.
I should note that for anyone looking for the function/capabilities (
without any concern of size/WAF), I believe if you are spending over $100 (as I was), your best option is to pony up $150 for refurbbed AVR from Accessories4Less like this one which has a legitimate 90 WPC rating and add a $15 BT receiver:
https://www.accessories4less.com/make-a-store/item/intdtr203/integra-dtr-20.3-5.2-ch-x-90-watts-thx-networking-a/v-receiver/1.html
Of course, the Nobsound at $33 (which includes BT) is insanely cheap and it is hard to believe it functions without any egregious compromises, so it'll be interesting to see if this technology continues to gain a foothold in the market and becomes a serious contender!
Edit: link to Nobsound amp reviewed above:
https://www.amazon.com/Nobsound-NS-10G-Bluetooth-Digital-Amplifier/dp/B01MS739KX/ref=sr_1_13?s=electronics&ie=UTF8&qid=1523292929&sr=1-13&keywords=nobsound+amplifier