Hi Peasrule, Yes, you can select the impedance for each cab you have connected to the speaker cab outs 1-4. No issue with playing the 16 ohm and the 8 ohm cabs simultaneously with one amp, the ZMACS will automatically switch the impedance for the amplifier when both cabs are selected, in this case down to 4 ohms even though the combination of a 16 ohm and a 8 ohm speaker cab does not create a 4 ohm load exactly, (around 5.3 ohms). So yes the ZMACS can definitely allow you to mix and match speaker cabs easily and safely. Hope that helps. Cheers! Gil