There was a guy walking around with one of these last summer at a local fest I was at, it was loud as fuck.

also, it's on sale for $70 right now! normally $200

http://www.amazon.com/Eton-Soulra-Powered-System-iPhone/dp/B004YAVDTE/ref=sr_1_9?ie=UTF8&qid=1428347674&sr=8-9&keywords=eton