Plugins and Themes (setting a class)

I was wondering which plugin to use. I started with appointments, but then not sure if to go with this one or Events, or the Calendar (although I do not think I will incorporate buddy press.

I think each one works great, they look great at this point, haven't installed or tried to use them.

If I have classes, and I would like for people to click on the calendar and sign up for the class themselves, and paying along the way after they finish, which one of these plugins would you recommend.

Which one of your themes would better compliment one of these plugins...

Oh, and by the way, the demo site on appointments...what theme is that one?

Or does appointment come with it's own built in theme?