Well just my 2 cents, I bought the Torx speakers off Amazon, $70. 3M adhesive to stick it inside the helmet, they're super thin and have great bass for such tiny speakers. Then I just taped a cheap waterproof mp3 player to the outside of my helmet. I just switched from earbuds cause they'd always shift and fall out. But hey, whatever floats your goat. I could throw up a picture if you want to see what I'm talking about.

Edit: Here's the speakers, http://www.amazon.com/gp/aw/d/B004I6HOQA/ref=mp_s_a_1_1?qid=1421344123&sr=8-1&pi=AC_SY200_QL40