Comment by bigiain

I'm leaning very much towards a Vagrant/Ansible setup to provision/deploy/configure instances across a range of VPS providers. I'm actively testing with DigitalOcean/Linode/AWS right now, spinning up Ubuntu 12LTS and 13 instances both locally (in VirtualBox) and remotely, and it's looking very promising. It'll only get you 1,2, and 4 out of your list though – but does have the big advantage of not suffering "lockin" to any of the VPS vendors. It also gives me really easy local Vagrant/VirtualBox development, test, and A environments – with very high assurance that they're all sensible replications of the deployed environments.

If your app/service is architected to make spinning up a new 1G or 2G instance when your 512M one is running short of resources, "faking" 3 would work. I'm not sure where I'd start looking if I needed a web interface for it all though…