Problem getting surround to work with Win7 and SPDIF on a mac mini

I have just gotten a Mac Mini 2011 model and have installed windows 7 on it. Previously I have had the sound card decode the multi channel sound and used my ageing amp as a power amp only. The mini does not sport analog connections for 6 channels, so I have resorted to use a toslink to the amp and let it decode dts/dd. Setting up the sound in control panel does not go well, as when I test the dts and dd, the sound for the center and rear speakers comes out of the main speakers. Same problem in WMC. The subwoofer works fine. I have tried with sharks007 and set it up to pass tru but it does not help. My amp is not an advanced one and the speakers rear and center work fine when fed an analog signal to the amp.

Any ideas?
Should I bust buy an external sound card with discrete analog outputs? Which?

I have come a little further. The test stuff in the control panel for DTS and DD does not give the correct sound, why I can deduce that the problem is in windows and/or the amp. The last I deem to be less likely, but I will test it with a different input and the old htpc and see if that helps.

Alternatively I could get a sound blaster x-fi 5.1 surround sund pro or a used extigy as external sound card. I havre tried to find M-Audio model that will output 5.1 as I have been quite happy with the revolution 7.1, but no such luck.

Problem solved. It was a setting on the amp.