S/pdif out only works on headphone and 2 speakers

Hi to all, especially to who has a soundcard with optical output.

I have a big problem, I can’t listen my DVDs in DD 5.1 using the S/PDIF Playback, because the driver doesn’t let me do it! Here the details:

My soundcard: Typhoon Acoutsic Six 5+1

My YAMAHA amplifier: http://www.homecinemachoice.com/testbench/frame.html?http://www.homecinemachoice.com/testbench/Amplifiers/Yamaha/YamahaRX-V795.shtml
(I have a home theatre set of speakers and I can play in DD 5.1 using my home DVD player)

My soundcard is connected to my amplifier using the optical-output (optical cable).
I can play stereo music, setting the speakers to “2”… but if i select “5.1”, I can’t have the S/PDIF playback, the checkbox disappears.

In fact, when I open the Mixer > Advanced > Speakers > there is a checkbox called:

“S/PDIF Playback - S/PDIF OUT only works on Headphone and 2 Speakers”

I guess this is a copy protection system, so for me it’s impossible to configure the soundcard in order to listen my DVDs in dolby digital 5.1 using my sound system.

Isn’t there a way to crack/hack the driver in order to let the S/PDIF playback work also in Dolby Digital 5.1?

Thanks for letting me know whatever would help me to achieve my goal to listen my DVDs in DD 5.1 using the optical output.

If you want I’ll also post a screenshot of that damn “Speakers” tab in the Mixer settings.