The Bose Compact carries so well, and has such clarity, that in larger situations, perhaps a better "add on" would be an additional bass amp or dedicated sub. The top end is almost always loud enough and will carry because of the design. Bass is what is usually missed in larger situations. I have a small 150watt bass amp in the van at all times ( mostly as backup ) just in case I need that extra "punch" that some younger crowds equate with quality.
BTW - I only used it once, and it was outdoors.