. It would be great to find a small, battery-powered device that would play at a reasonable volume when camping alone.
There are lots of small devices to choose from.
There's something to remember: Due to the immutable laws of physics, the smaller the loudspeaker, the less loud it can be. Less ability to go loud equals less dynamic range. Less dynamic range equals audible compression, which makes the music reproduce kind of flat and lifeless.
Pop music that is played at a constant volume level survives compression better than dynamic classical. When a FFF cymbal crash in an orchestral piece is the same loudness as a PP solo clarinet, it kind of sucks the life out of the music.
Now, if you take one of the new miracle mini units and place it next to your head in the tent, it'll simulate a nice hifi stereo.
Next best would be to place the small unit(s) inside a vehicle facing out. The vehicle interior becomes a room to generate bass resonances and gives a pleasing "rich" sound.
I've done this with the Bose Sound Link units (2 units tricked into being the left and right sides of stereo) placed in the back of my 4Runner with the back hatch open. I sit 5 or 10 feet away and the sound is pleasant....but...because they are small speakers, they never reproduce anything with full dynamic range.
A well-designed boom box...something with 6 inch or larger woofers, maybe, should give the best sound with the least rigamarole: They're not small, but because of it's size it 'brings the room with itself' and is capable of fairly nice sound when placed out in the open, like on the camp table.