So this is what I came up with and I'm so happy with it that I thought I'd share. It doesn't require any sewing so if you can't sew and don't want to experiment, you can use snaps which are very easy to put together. Keep in mind when you make your choice that the sewing is only one option and it's fairly simple. Sewing a few particular peices will make the system virtually unnoticeable to you when wearing the hoodie, the snaps are just a bit more bulky.
Another thing to think about is that once built, this system will be quickly adaptable to the next hoodie you buy (I tend to go through them rather fast), you will just need to put a few snaps into your new hoodie.
For anyone who watches the video, I wanted to explain that the volume on the speakers was down half way so I could talk over it. I was very impressed with the sound out of those small speakers, and would recommend them for this project.