If you mix in 5.1 or 7.1, keep in mind cds cannot support this type of encoding. You would have to create a SA-CD, HD-CD, or DVD-A for this type of mixing to play the audio properly. Currently, there is not blank SA-CD or HD-cd media available in the market.
I will sometimes mix in 7.1...although to truly appreciate the work i've done, I have to listen to it in my studio. If I mix in 5.1 I can burn it to a DVD to play at home through my surround sound. It sounds pretty sweet - unfortunately, it's really too much work and it takes too much time/energy for it to be worth it personally.
I am interested to hear how things turn out for you.
Good Luck.