Audigy 2 = CMSS with 2/2.1 CH Speakers and Dolby5.1 from my Xbox360???

I am outputting Dolby Digital 5.1 from my Xbox360 into my Creative Audigy 2.

In the settings I have Dolby Digital and Dolby EX set to Auto, and I have CMSS turned on. When I change the settings to Headphones instead of 2/2.1CH, the Surround Sound emulation becomes very obvious (with front sounds sounding much different from the rear) - but when I change it back to 2/2.1, I have a hard time telling whether the CMSS is still emulating the 5.1CH input on the speakers (even with headphones on).

So my question, with my Audigy2, if I have the Dolby Digital decoding set to Auto, CMSS1 turned on, and speakers set to 2/2.1: Am I getting an emulated 5.1 surround sound experience? Or does it only work when I have speakers set to 'Headphones'?