Unfortunately, it is not possible to install cPanel and Plesk on the same server. When deciding what control panel you want, look at the features that each control panel provides, and see which one willl suit your needs better. both are tightly integrated with the underlying services, but cPanel is more complex, but more powerful. Plesk provides all the tools you'll need to get your server up and running without much of the "learning curve" that cPanel has.

cPanel is better documented; it is easier to find answers through Google when you need them, but for the most part, Plesk doesn't reqire as much documentation as cPanel.

Anyways, take a look at the choices available. Right now, Spry is including all control panels for free. Spry is even ready to help you migrate to another control panel (should you fiind that your first pick wasn't right). The rub is that we're only going to do this once. If you decide you liked the first control panel better, or would like to swithc yet agin to another control panel, we will charge for it.