Can you run Lion os and Lion Server os on the same Mac mini?

I'm a windows convert to Mac and I'm interested in running a standard Lion Client, but at the same time running Lion Server on the same Mac Mini (Server Edition). My needs for the Lion Server OS is to handle e-mail, a Web Site, and file sharing between the server to a secondary PC, iPad, and iPhone. But at the same time I wish to dive into the Mac (Apple) experience. I just wish to be able to do this on the same machine.

As a secondary question, is it possible to merge two different iTune Accounts into one? Is it possible to share items purchased on one iTunes account with an iPad that is tied to a different iTunes Account?