is it possible to install a full working OS with a webserver, db, and all needed stuff on an EBS storage?

If so, would I immediatly gain benefits by mounting this EBS on a better instance?

Otherwise (if I cannot install a complete image, or if you don't think it's reasonable) can I install the software so that I only need to mount the EBS on a new instance to have it working?

I purchased a Medium Reserved Instance, but when there will be the need to get a better instance I'd like to move the whole db/website, I'd simply buy a better instance and then attach the EBS. Is it possibile? I'm imaging about it like an hard drive that would be mounted on a better server. Of course, more RAM would allow me to increase caching limits, and that's ok, but I don't want to reinstall anything (the main website is a magentocommerce and it's pretty painful to move it).

P.S. is the Standard EBS (100 IOPS) valid or do I need to choose a Provisioned IOPS (up to 1000 IOPS)?