Dedicated hosting services primarily differ from managed hosting services in that managed hosting services usually offer more support and other services. As such, managed hosting is targeted towards clients with less technical knowledge, whereas dedicated hosting services, or unmanaged hosting services, are suitable for web development and system administrator professionals.
If you want top-of-the-line servers running a Linux operating system and plan on managing the network yourself, InMotion Hosting is a good option in the $100 ballpark. The company offers excellent support and exceptional server power. If you prefer to have your web host manage your servers for you, InMotion Hosting offers managed services, as well.
The answer to this question largely depends on two factors. Are you new to server technology and not very interested? In this case, Windows is the easiest option to get where you want to go. Do you already have experience with Linux or would you like to familiarize yourself with this operating system? If so, Linux gives you more freedoms to configure your server, and you will be using an operating system that is less vulnerable to attacks from the Internet. Linux is also open source and therefore free.