This is my scenario.

To start with, I will have 50 WordPress Client blogs heavily customized with plugins. Expect around 50-500 visitors a day for each blog.

I will also have each blog set up with a custom PHPlist (or similar open source) email autoresponder. I will also need to set up a separate server for sending out the emails. (Kind of like using Aweber, but self hosted). Let’s assume we’ll send out 500-1000 emails each week to consumers with each blogs.

I might also have custom tracking options such as those found in Google Analytics for each blog. But it will be in house applications.

What kind of hosting do I need for this?

Reliability and up-time is of utmost importance since these are business clients.

Should I go with a fully managed set up or is it better to hire a webmaster full time and go for an unmanaged server?

Is it possible to set this up using Amazon cloud so that it becomes scalable?

Please advice. Any help regarding monthly cost will also help.

Thank you.