WickedWesticle says:
They don't offer the stupidly huge range of stores that some other places do but I doubt anyone would buy this kinda stuff from anywhere other than iTunes, Amazon, Play or 7digital.
That's all you need really, and Spotify
I'm not sure how those places work though, how will people come across your (relatively unknown) band? Does it work on a "if you like this, you'll like these" principle?