I am new to cloud computing, so please bear with me here. I have an existing ASP.NET application with SQL Server 2008 hosted on a Virtual Private Server. Here's what it briefly does:

1. The front end accepts user's requests and adds them to a DB table
2. A Windows Service running in the background picks up the request, processes it and sets a flag.
3. The Windows Services also creates a file for the user to download.
4. User downloads file

I'd like to move this web application with the service to the cloud. The architecture I envision is that I'll have 1 Web server in which I will install the front end and the windows service. I'll also have a cloud files server for file storage. The windows service should somehow create a file and transfer it to the cloud file server (I assume this is possible?)

My questions:

1. Does the architecture look like I am going in the right direction?
2. I know Amazon has been providing cloud services for a long time. If I want to do minimal changes to my application, should I go with Amazon, Rackspace, Azure or some other provider?
3. I understand that I would not only pay for file storage and web server but also for the bandwidth of users downloading the file and the windows servic uploading the file to the cloud server. Can I assume these costs are negligible? Should I go with VPS + Cloud Files combination to begin with?

Any other thoughts/suggestions?