I don't have a desktop manager installed (and I don't want to). After logging in through the terminal I use startx to start the GUI. I have entries in ~/.xinitrc for my GUI sessions. Right now I have xmonad in there, but sometimes I want to run a GNOME session, and sometimes a KDE session. I used to edit ~/.xinitrc for that purpose, but I think there should be a more elegant way (something like using alternate configurations). However, I can't find anything in man startx or man xinit.
I plan to have several configuration files (one for each GUI session), and then tell startx to load them when I want. How can I do that?