HI David it is actually very possible to do. all you have to do is select 5.1 or multi track audio when you first create your sequence you set this up in the Tracks tab of the sequence settings. if you have already finished your project and want to export in 5.,1 then create a new sequence and set your video presets so it matches your project. then click on the tracks tab, you can then select 5.1 or multi track audio you can then select the number of tracks and pre name them. then just copy and past your stereo sequence into the new one and export away you will now find in the export window on the audio tab that you can export 5.1 or how ever you decided to set it up.
cheers.