Here is one way you can do this ...
make a copy of your XF86Config file with the Mode set the way you want it in /etc/X11 named XF86Config1
now you can start a server on another virtual display like this...
startx -- :1 -xf86config XF86Config1
Or something like this..
startx -e mplayer dvd://1 -- :1 -xf86config XF86Config1
Switch back to the first server with ctrl_alt_F7 and back to the second with ctrl_alt_F8
start up as many as 6 servers if you want.