If you're in the one of lucky countries (or have credit card from one of them) I'd suggest Spotify, their client is marvelous (the best UI for a music player ev

If you're in the one of lucky countries (or have credit card from one of them) I'd suggest Spotify, their client is marvelous (the best UI for a music player ever and also very fast), supports playing local files and since last version also syncing with Apple devices (maybe some others too, haven't had occasion to check).