You can do that by purchasing another sound card and switch between the built in and the add in card from inside the Windows. But you can't have 2 outputs at the same time but you can make what you said but you'll have to insert the jacks every time.
Elaborate farther, please. More information needed? The sound card is onboard Realtek something....... Nvm My PC is an HP Pavilion a819n.
So for 2 outputs I'd wish to plug in my speakers to the one labeled "Center" and my headphones plugged into "Front Speaker out" because plugging into the headphones jack seems to disable all other ports.
Edit: After a short time of messing with the settings everywhere I enabled 7.1 Surround sound and set my media player to output only at 2.1 channels. That made the music come out of my speakers while my headphones worked for the game only.