Here's what I've done for years now. I use it for both dirtbiking and snowmobiling and it works awesome. Bluetooth is no good up in the mountains as the battery will just wear down really fast due to the cold. Find an Ipod Shuffle and Velcro it under your visor. There's kind of a little pocket in my dirtbike helmet so I didn't have to cut any of the foam away for the speakers but had to a little in my 509 helmet so they would fit without touching my ears.
Pretty cheap way to go and really effective. No one but you can hear your music either. The link below are the speakers that I first got and used and they are great. I then got the Uclear helmet communication system so I could talk with my son while we ride dirtbikes together and those speakers are awesome. Way better quality and much more base and you can talk and listen to the music at the same time. However, it uses bluetooth for the communication and music to work. I've never used the communication part while snowmobiling because we all use the BCA link system and just plug the Uclear speakers into the Ipod shuffle so don't have to use the bluetooth part.
I also have the Sweet MTNTK sound system as well but can hear the music just fine over the turbo and motor and yet can also hear the sled and motor just fine. Don't ever feel like i'm tuned out and don't know what's going on with the sled at the same time.
Amazon product ASIN B00OTWLKMW
