Six channel in mainstream commercial releases is the same as 5.1. The .1 indicates that it is bandwidth limited as opposed to full range.
There are some releases that utilize 6 full range channels from MDG, Tacet and Chesky.
As far as sampling frequencies and depths go, higher is better to a certain point. Above that, it's as much bragging rights as anything else.
The Linkin Park disc is comprised of digital masters which were originally captured at 48kHz, and as such the producers and artist came to the conclusion that there was no point to a 96k release.
Hopefully this answers your questions, and if not, respond back
Cheers,