Connect the HTPC to the TV, capture the EDID and setup audio/video as you like. Reconnect HTPC to AVR and use.
I have solved it today, i add a HDMI switch and justlet the signal pass through it. And it works great, so now i use PCM on the AVR. But from what I understand, it is at least as good as DD and DTS as it is in raw format. So now i have it like this without Toslink: PC->HDMI SWITCH->AVR->TV. So now i can set the volume remotely again. Thanks for all ideas.