[Farhoof]

The Emotiva is just a power amp right? Which is fed (hardwired) by the Marantz AV receiver?
In that case maybe the Marantz has a multichannel analog input you can use to hook up your audio interface. This way you can switch between your Protools output and other media devices.
Keep in mind, using a multichannel analog input on pretty much any AV receiver will bypass all the processing features on the device (like room eq, etc), as most receiver only have AD converters for stereo sources.

Another way would be to use a MTRX as your monitor controller/volume/room eq, etc, and feed it with the Marantz output for your Bluray/Game/Homecinema stuff, and output to the power amps for the speakers. You will need a ton of AD/DA though for the MTRX which can get expensive.