startx without messing with .xinitrc

Is there any parameter I can give to startx to specify whether to launch GNOME or KDE??
The man page looks like there is, but I'm sooooooo confused, it's not even funny.

So...help?
Thanks :D.

For those of you who are curious.
Just init 5.
Yes, you have to re-login...but you get the login screen.
X_X, thanks for everyone's help :D.