Using iMac in Home Cinema I am currently considering buying an iMac 27" to replace my PC, and also to have at the centre of my home cinema/media system.  

The iMac would be used to play DVDs, stream video, play CDs, MP3s etc.

I want to send both the video and audio to a Home Cinema Reciever, ideally all through an HDMI cable (avoiding a separate cable for the audio), connected to the iMac via a MDP to HDMI converter.  The video is then relayed on to my projector by HDMI from the Home Cinema Reciever.

I have a few questions that aren't clearly answered by the Apple specs:


Will DTS/Dolby audio be sent via the Thunderbolt/MDP port to the Home Cinema Reciever through the HDMI cable?  Apple say audio is sent, but that could just mean stereo!
I read somewhere that for HDMI with Audio it was necessary to mirror the display.  The iMac will be visible from the seating for viewing the projected image.  I will want to blank the iMac screen and just use the projector when watching movies etc.  I don't want to see a smaller version of what is projected!  
Will I be able to output audio to the Home Cinema Reciever when playing MP3s etc through iTunes or another media player?
According to Apple Support you can get MDP to HDMI adapters with sound support from Griffin and Moshi.


According to http://store.moshimonde.com/faq-minidisplayport-to-hdmi:


  
  Which audio formats are supported via Apple's Mini DisplayPort?
  
  
  Recent Apple/Mac models (see above table for compatibility list) do
  support multi-channel 24-bit digital audio output such as Dolby
  Digital Surround and DTS as well as 2-channel stereo. Our Mini
  DisplayPort to HDMI adapter is a translation device that would then
  pass the audio bit stream unaltered to your AV receiver or TV for
  further processing.



I don't see why that would be necessary.
As long as audio output is set to HDMI.