Jim, as you own the Soundlink II, why don't you use Oluv's switcher to test it against the Beolit?

http://switcher.oluvsgadgets.net

It's a reliable comparison tool, I can confirm that those speakers I have tested are properly recorded there and give a good idea of how loud they are. Oluv has recorded all those speakers with binaural microphones under identical conditions.
Select Beolit 15 and Soundlink III as the two speakers to be compared, then click on one of the genres listed at "maximum volume", and listen to it with headphones. (There's hardly any difference between Soundlink I, II and III).
I think even the iLoud is in the list...