Low and mid-line JBL's may indeed not impress, but spend the money on the SRX series, and you understand why they have the reputation......

You can get concert-level volume from their small 12" and horn SRX with a subwoofer, at perfect clarity and reliability......

Also, if you are doing pretty small jobs, the Logitech Z2300s do a really good job. Quick setup and PLENTY of bottom.
Logitech has the very best support you will ever find.
DonM

I've played all kinds of gigs with the small alesis mixer and the 10" powered JBL speakers and it's worked out fine.