There is another way: decode it in your media centre and send it analogue to your amplifier. Remember when media centres were actually capable? It has to be decoded to analogue somewhere. Dolby digital and DTS are not the only way to get surround (also good stereo is better than shit surround, but let's assume you mean good surround).

The whole thing about HDMI is a circular argument. You can only use HDMI because you can only use HDMI. There's nothing technical stopping another cable supporting this stuff. That was my original point. We're in this situation for silly reasons, not technical reasons.