What is the simplest way of producing/exporting an in-the-box 5 track surround song ?

I have a 7.0 surround system in my theatre room in the basement that is currently not merged with my music-making setup that's elsewhere in the house.  But putting that aside, what's the easiest way to get multi-channel music that I've created using soft synths in Sonar to output in surround from my theater system ?

I have dvd and blu-ray recorders on my daw and 7.1 blu-ray player, receiver and speakers in the basement.  Which common format should I export to from Sonar and write to a dvd or blu-ray disc so that it'll be played properly by the blu-ray player ?

I'm amazed everyday by the sound of music in surround, even in an untreated small room.  But I can't make up my mind how to merge my two systems since I have a much better room upstairs (large, 9' ceiling, well lit) but can make more noise at night downstairs where the room is pretty bad (small, 7' ceiling and claustrophobic).

I would think you would need to get access to some encoding software, then run a stereo pair to an input on your home cinema system or cut to CD/DVD.  If you come up with a cheep encoder let me know SONAR did come with a trial encoder but the full price version was painfully damaging to finances.  

I have not actually done this in SONAR, but have seen it mentioned in passing (I think Craig mentioned this a while ago). SONAR does have a "Surround - 5.1" template at the bottom of the "New Project" dialog. I have not used this, but SONAR is indeed 5.1 capable. I wish I had more information, but at least that is a start.
 
FWIW, 2 comments... 1) some sound systems (even Windows) will simulate surround even from a stereo file... this may be the more elegant solution... 2) I have dabbled with 5.1 in Adobe Audition, and although got great results that would blow your head off, these files are truly massive (like 200+MB each), so I have always resorted to #1.

Yup... my interface, the Focusrite Saffire was touted as a 7.1 capable interface for film and gaming music....
I work in stereo and have no clue how to do that surround sound stuff.