Hi
See
here
HDMI is more about audio than video which makes it important to look for an AV amp with an HDMI repeater rather than an HDMI switch, as explained in the above post. This means amps can accept and process audio via HDMI and as HD players can nearly all decode the new HD audio CODECs and send it to the amp via HDMI as MPCM (Multi Channel Linear PCM data). Some amps can support upto 6 channel MPCM data over HDMI, others up to 8 channel. Amps with HDMI switches can NOT handle HDMI audio at all. HDMI v 1.1 is the minimum requirement for MPCM.
Although HDMI 1.3 will be able to carry HD Audio bitstream signals (before decoding) it is very unlikly that the record labels and studios will allow this to happen. This means most amps will acept HD audio signals as MPCM.
Regards
Chris Moseley
Yamaha UK