Small Bedroom Tube Amp

Glow
MiniWatt
TecOn

All in the $250 range used.  I own all 3.

I have an APPJ in black with low hours and original shipping box that I’m not using. Let me know if you are interested. 

Dayens Ampino. It will give you anything an inexpensive tube amp will without the hassle of tubes. It's also tiny in size and fits your application perfectly. It's the closest to tube sound I've found yet in inexpensive solid state. 

https://www.audiothesis.com/product-page/dayens-ampino-integrated-amplifier

It depends on how you're planning to use it and what sources you'll be using. This may sound like a completely different option but in my opinion, the simplest approach for a bedroom system is a Bluesound Sound Bar. It sounds great, and its an all-in-one system allowing wireless streaming of high quality content from many popular cloud music content services, e.g., Tidal, Spotify, etc. And the best part is you can control it while lying down on your bed. Look it up.

"  It depends on how you're planning to use it"

the OP said :

"   I want to mellow out music when putting the little one to sleep."