I know there are ways to install kde on a standard ubuntu system which is strictly gnome based, or at least there used to be. Once installed you have the option in your login window to go into kde or gnome. Here's a link describing the process in detail:
Note some of the problems and issues you can run into mentioned in the article.
In general, you can run kde apps in gnome and gnome apps in kde; you just have to have all the necessary libraries and dependencies installed. If you install through apt/synaptic that would be done automatically. For example, I know the kde cd burning app, k3b, is available in ubuntu and commonly installed and used in the gnome based environment of ubuntu. If you go through the above kde install and boot into gnome, you should be able to run the kde file browser, konqueror, within gnome and it should behave like I described in my prior post. However, only the kde apps would be listed in the menus for opening your multiple files.