I don't know how good they are, but you could check out the bottlehead kits. I have not heard them nor tried to build them, so I'm not much help there, but I though you might want to take a look.

I'd like to monitor the amount of power (in watts) going into my speakers. I'm not concerned about over driving them or anything, I'm just curious how much power I'm actually using. I connected a volt ...

Build a mini amplifier using simple electronic components. A practical DIY electronics project perfect for beginners, students, or hobbyists who love sound experiments. #MiniAmplifierDIY ...