How to design an application like SoundCloud?

I am looking for recommendations on how to design an application like SoundCloud.

I am planning to develop an application that will be available across multiple platforms. I want to start developing for Android because that's what I am most comfortable with. The best example I can give ye to show what I want is an application like SoundCloud.

I am looking for advice on how to design such an application. So far I have a "Sign up with Google" button on one of my activities. New users would click this button to register with their Google account information. I also created a Google Developers Console project for this application.

(1) After retrieving the users basic profile information which will be used to create on account for them, where would I save it? My thoughts on this were to use Amazon Web Service or Google Cloud Messaging and use their virtual servers.

(2) What service is better for a SoundCloud-like application, Amazon Web Service or Google Cloud Messaging?

(3) My thoughts so far is that I'll have to develop my own API to interact with my servers. Where would the API code be stored?