Is there an open source CMS out there that can handle my needs while still being user-friendly?
Yes, but I don't have a clue what it is. It's like me telling you what kind of car you should drive. I can tell you that you should use Exponent or Website Baker, but you may not like them.
So why don't you visit Opensource CMS where you can try out the ones you have heard about and others that few people have heard about? Opensourcecms.com has live demos set up and you can play with all you want, post spam to, and do anything you want with. This is because the system reloads them after a set time period allowing new visitors to work with a fresh copy.
They also have demos of different blogs, forums, groupware, image galleries, learning software, shopping carts, and Wikis...!
You can listen to the advice of others, but most people starting using one CMS or another and to them, that one is the best. While some are more popular than others, that can change. PHP-Nuke use to be the CMS of choice and now I don't hear anyone talking about it... :-)