WordPress Theme Demo Site

I am trying to create a site in which I can display some themes on. I basically want to give the clients the choice of there layout before I start building out the site. I like the options the WooThemes offers at demo.woothemes.com. I want the options to have both a theme chooser as well as a style chooser. This is where I am drawing a blank. I could use the Theme Demo Bar plugin, but it doesn’t have a style sheet changer. What do you think is the best solution for this?