Gary, you know I love the Bose Compacts, and I always use two together in stereo, BUT, to handle 500 people they would have to be seated and fairly quite. I really pushed mine to handle a rather rowdy Mardi Gras party with about 250 people. It's the only time I have missed the bigger L1 system.
Now, a one or two of the bigger L1s and a sub or two and you can handle anything any of us are liable to come across. But 90+ percent of the time it would be overkill.
Plus I like the fact that the Compacts are so easily positioned. I generally use each with one extension, but if I'm at crowd level (not on bandstand) I sometimes use both extensions. Position one to each side and slightly behind, and I can hear exactly what the crowd hears (for better or for worse!)