The 3-watt PAM8403 is considerably powerful; I found pairing it with a 47-ohm resistor keeps it louder than the gameboy color's default, but still comfortable on the ears.
Nice sound output! Easy to install and worth the cost to install.
All Gameboy's suffer from low volume, and once you add this tonyou build you'll wonder how you ever loved without it!
Definitely recommend this easy to understand instruction, easy to assemble, good quality and sure to give Gameboy a rock and roll sound!