Review: Global Delight's Boom - boost mac's volume

Sometimes some youtube clips, movies or podcast have their audio recorded really low. My Macbooks' sound is not really strong, so when I listen to such a video I struggle to catch the speech - especially when I'm in the shower.

Global Delight has created Boom. It costs $4.99. A software solution to such a problem - it can boost the volume up to 400% and has a system-wide equalizer:

Here's an indian presenting it: