Amp for mono speaker

Hi All,

Bit of a noob here regarding audio. I am currently planning to create an Arduino powered radio for one of my vintage cars, and I am looking for a small amplifier for it. It will only run 1 speaker of 4 ohm, 25 watts. I would like to have it all in 1 unit, so not in a seperate case.

If you guys could perhaps give me some suggestions that would be helpful. Thanks in advance.