I'm trying to get my multi-room setup switched over to use HDMI for audio as well as video. Two of my components are Component + SPDIF only (cable box and Xbox 360). So I got this thing on ebay: (search for item 180204876881)

Stereo is working fine, but if I turn 5.1 on either source device I get no sound. Both TVs have optical outputs for passing on 5.1 to a receiver. Those aren't working either. One of the TVs I know for sure is supposed to downmix Dolby 5.1. So I should be hearing something, right?

Any ideas?