You might find this an interesting read. The potential victor at 96kHz is a chap named Mark McKinnon-Bassett, who has a PhD based on listening and ear training. -
http://www.trustmeimascientist.com/2...mount-everest/
What plugins are you running? There is a very good chance that they are causing the skew in CPU usage. I know at Avid Eleven MKII for example is particularly bad at spreading the load over multiple CPUs. You may want to try removing all the plugins, then experiment with different ones to see how they effect the CPU load. In some cases processes will be serial rather than parallel, and you will benefit from having higher single core CPU speeds than more CPU cores. Just personally, I don't think there is any real benefit using 192kHz sample rates.