I use similar tactics in my car.
I live a block from the local high school, right on the main drag - the perfect place to encounter window-rattling automotive sound systems. Since I have any number of better things to do with my money than buy one of the damn things myself, I rigged up a homebrew countermeasure. The main components are a 250-watt power inverter ($30 at Wal-Mart and useful for any number of things), a couple of RCA adapters ($6 at Radio Shack), a 15-foot instrument cable (already had it), and a Peavy PA with onboard amp and EQ (already had it). I also put together a mix of my favorite "thunder" music - "Flight of the Valkyries," "Hall of the Mountain King," Williams' "Imperial March," that sort of stuff.
When one of these little punks pulls up beside me, bass blasting so loud that I can hear it through two layers of glass, I just reach down and turn the inverter on. "Toccata and Fugue" sounds amazing
through a 200-watt, 12-inch woofer.
The system has also come in handy a couple other times - I used it to play music in last year's Old Settlers' Days parade, and it's been called into service for live sound at a couple outdoor shows. And when I need any of the components for another purpose, it can be taken apart in a matter of seconds - nothing's hardwired.
_________________"Vox populi? Vox humbug!"
- William Tecumseh Sherman