Interested in what folks are using for a portable solution (where there is no power)?
I use one of these ( I have the 12inch speaker, rather than 15 inch). The battery charge lasts about 8 hours.
It comes with 2 radio mikes ( which I assumed would be cheap and nasty, but are, in fact, quite good ) or you can jack a wired one into the back. The 12inch version costs about 170 pounds.