For shear volume, The Block Rocker by Ion. Costco has these on sale for $120. I have one I take to the beach, drowns out the wind and the waves.
http://www.ionaudio.com/products/details/block-rocker-am-fm
for the next couple of days (until 7/31, I believe), these are also on sale at
Sams Club for $120, can order online and select store pickup if your local store has them in stock..... the
"Job Rocker" is also $120, but can only be bought at the store..... as far as I can see, the differences are that the Block Rocker has a USB port and wheels, and the Job Rocker, since it's meant to be used on job sites, has a couple of extra AC outlets (that only work when it's plugged in) but no USB, and supposedly an extra 25ft of bluetooth coverage..... same 50W speaker..... also, only available online at Sams is the
"Road Rocker" for $75..... bluetooth and usb port, but no mention of speaker wattage anywhere that I can see.....