Server system administrator

Hi we need a company to take care of our server. The responsibilities will be:
1) to take backups of the server 3 times per week
2) take care about the alerts of the site and fixes them quick
3) transfer sites from one server to another
4) check for errors
5) check for email erros
6) improve the server functionalities and hardware

We need proposals with techical analysis, cost and a portfolio from previous works. We will not check proposals without these infos.