Why/when "Expand 6.1 to 7.1" vs. "Enable Mixing"

[Nerva]

Is there a reason to use "Expand 6.1 to 7.1" vs. "Enable Mixing" with the Output Speaker Configuration being either 5.1 or 7.1?

I have a PC with 5.1 and a HTPC with 7.1. I'm just thinking, if I'm already using the mixer with my 7.1 HPTC and I'm playing a 6.1 file, wouldn't the mixer serve the same function as the "Expand 6.1 to 7.1" option? And if I'm playing the same 6.1 file on my 5.1 PC, would the mixer properly split the rear channel and send it to both sides even if the "Expand 6.1 to 7.1" isn't enabled?

[clsid]

You enable the mixer if you want LAV to do the mixing. Otherwise mixing is done by Windows or your receiver. In your case simply select 5.1 or 7.1 depending on your system.

"Expand 6.1 to 7.1" exists for the situation where mixing in LAV is disabled and your receiver is not capable of handling 6.1.

[ashlar42]

My Yamaha receiver, for instance, was uncapable of handling 6.1 signals, resulting in no sound, activating "Expand 6.1 to 7.1" solved that.