I like litestep a whole lot better than explorer. Likestep is much better on resources depending on the theme but it should run great on a p3800. To me that's not exactly slow. Read more about litestep before you jump right in though, especially if you're going to start theming. The new installer will install it perfectly on your system and the simplicity theme that comes with it is beautiful. Just play around with that and other OTS themes and that should give you a good feel.