Surprisingly powerfull
The build in amplifier of my old Monitor Audio Radius 360 subwoofer died. In stead I connected the driver unit directly to this little amplifier. (so I used the sub as a passive subwoofer). Powered by a 6 ampere 24V SMPS:
Surprise: bass sounded deeper, less boomy/muddled and more powerfull than with the original build in amplifier of the subwoofer!
Thanks to audiphonics.

ampli sub
Petit mais costaud ! Bon renfort de basses nettes et pas ”boursouflées” . Super rapport qualité prix

So far so good!
I bought this to use with a 10" passive DIY sub as part of my "desktop" setup. And it seems to get the job done admirably in spite of its low price and diminutive size. I can't really say anything about its max power though, since this is very nearfield listening at low to moderate volumes. Even the power supply I use is only 12V 5A, since I had an extra laying around. More than enough for this use case in any case.

One minor minus is that turning the volume pot functions as the on/off for the device, which is a hassle when you want to keep it at a preset level but would still like to turn it off. Also it has quite a bit of "play" before it actually turns the thing on/off, and doesn't really feel that great to turn.

One other thing to note is that this indeed takes a 3.5mm stereo plug and combines the channels for output. The 60W subwoofer amp stated that, while this one didn't.

All in all a handy device well worth its price for smaller-scale applications.