Hi,
Lowering the Max Voices in the settings of the Spitfire Audio Player to 45, or 64 fixed the CPU overload issues when using more than one mic.
If you are experiencing heavy CPU usage, or spikes, lower your Max Voices setting to 64. and test to see if that fixed the issue.
I'm also getting better performance now when using the AR-2 Strings, which sound awesome ! I think it should improve any of their libraries work better.
Cheers,
Muziksculp