The MIR will most certainly need its own machine (try to run more than 20 unoptimized convolutions on your most recent CPU, and tell us how you scucceeded...). Steff3 is right: The later we release, the stronger the available CPUs will be (and the luckier are our users with the MIR's performance [+o(] )
Regarding mixing and additional FX like dynamics or EQs: You will have the opportunity to integrate your plugins into the MIR itself, as long as they comply tightly with the VST-standard tightly. As i wrote before, the MIR is meant to be a mixing-frontend, not just "another" effect.
To Christian Marcussen: Spring would be the favorite release date for us, too, but we won't overhast it now in the final stage. So please don't count on it, and don't take this as an announcement.
Kind regards,