Cloud or In House Server

Hi All

I need some professional input. I'm trying to decide whether to build a nice server to handle my companies needs or should we look more toward cloud based solutions?

Ultimately, what I would like to do is have instant messaging, email, space for 2 or 4 shared folders, and space to backup information from a few other servers.(Oh, and something like active directory to help with user security).

I've been pricing cloud solutions but the cost seems to me to be a little high. Is it possible to have 1 server to handle all of these solutions or would I come out better looking into the cloud solutions?

Thanks for any input guys :o