Welcome ys_11062, thanks for your interest in Vienna MIR and MIR Pro.
You are most certainly aware of the fact that you will need a 64-bit OS to use MIR. 28 GB should be plenty for the typical "big" project, but maybe not when ProTools does a lot of RAM-intensive jobs too. 8 cores will make MIR happy, as long as you don't reach for really dense arrangements in multi-channel formats. The guidlines for optimum resource management will be in MIR Pro's manual (... please remember, we're still in Beta-phase).
BTW .... RAM size is not the only crucial parameter, but also its bus speed. The quite unusual size of 28 GB makes me suspect that there could be a bottleneck somewhere, depending in your specific configuration. - I would have to ask our local IT-gurus for an educated opinion, though. :-)