I'd recommend trying this out on another game before Doom hits the shelves. Many recent games (good ones that you should be playing while you wait for doom) have 3D sound options. Halo, Far Cry, Painkiller, Unreal Tournament 2004, all of them make full use of 3D sound cards.

Personally, I don't like the results of any of the "simulated" 3D sound selections I've heard. They all just sound weird and hollow to me, like I'm playing the game inside a large metal tube. Unless I've actually got the extra speakers, I make sure to uncheck the 3D sound option in the game before I play.