The key pairs are only required if you want to perform passwordless connections. If you use an ssh connection with the -X switch, you should be able to simply run your X applications (on the remote host) without having to modify the $DISPLAY variable. The ssh will have created $DISPLAY, setting it to something like "localhost:10.0". The X clients then use this to know where to send X traffic, and the ssh server tunnels it back to your local X server.
I'm not sure what arguments are known to startx. I think startx is nomally a shell script, so the answer is in the code. As such, you could probably customize it fairly easily to do what you want.
Last edited by theNbomr; 10-04-2007 at 01:36 PM.