No experience with headsets but my power bass 1200 sound bar is definitely loud enough. It is alittle big though.
Take the money and buy an intercom and car-to-car radio. Bluetooth the music into your helmet or headsets. It adds a whole new dimension to your riding being able to talk to your passenger and other riders around you while listening to music. Also, the rest of us don't have to listen to the blaring music that you are trying to drown out the sound of that sweet three-cylinder with!