you did not answer, Stereo of 5.1 or 7.1 ?
Good guess : what is more powerfull you Imac or the MacMini ? did you look at benchmarks ?
Did you understand that the Mac that is handling VE/MIR is doing all the work ?
If I look at my test piece in 7.1 using IAC on my 12 core/24 threads, Logic is using 60 % it is only sending midi to the VE/MIR and receiving the audio back from VE/MIR, VE+MIR is using up to 1500 %
VE+MIR is one process it is puting all the load on the CPU
If you put some instruments(EXS, Kontakt...) in Logic you will need to send them as Audio Input tracks to VE/MIR
SO IT IS THE MOST POWERFULL COMPUTER THAT MUST HANDLE VE/VI/AI/MIR
I really dont know if a Macmini or an I7 could do the job