There are a few low power amplifier boards available online (for me low power = can be powered by 5V or lower). In this video I'm testing two boards with the most common ICs i see in such boards (the 8002 and PAM8403)...

Introduction: 00:00
Measuring the 8002 board: 03:00
The PAM8403 board: 11:30

This video is more of a comparison of power requirements (measuring input current at 5V) and amplification.
I might make another video where i will connect the same speakers to both boards and purely subjectively try to compare which sounds better (obviously i don't have the equipment to measure the sound quality reliably).

As expected, the class D amplifier is more efficient (was getting about 12x amplification with load (4 ohm speaker) while with the 8002 i was getting 8x). The PAM8403 board also had stable amplification at all the frequencies while with the 8002 board the amplification was significantly lower with frequencies under 400 Hz...