I asked your question in a slightly different way in a recent exchange with Scott in Outlaw Customer Service. I asked how much current the 750 draws in idle, ie: when no signal is being driven from any channels. Here's the response:

"The Model 750 uses five separate bias circuits that could draw as much as 100
watts in standby mode."

The way I understand it, there is no mechanism by which the 750 could know that it is receiving DD or DTS, the only signals it sees are analog preamp output on each of it's 5 channels.

There are some amplifier designs that automatically power up a channel upon receiving a signal and shut down after a certain amount of time without a signal but I have only seen that design used in Subwoofers.

Re: Interconnects, I started with Moster Interlink 250 and switched to Audioquest after breaking the RCA connector on two of the Monster cables. I am very satisfied with the build quality and sound I get with the Audioquest. Specifically I'm using the Sidewinder for my sub connection and Copperhead for the rest. I got a good price at www.AudioAdvisor.com