Hi Joshua:
Technically, when calculating the impedance setting on the Internal Impedance matching Volume Controls you have to base everything on 8 ohms. If you have 4 pairs of 8 ohm speakers you set the jumper to pins 4 and 5 for 4X. If you had 3 pairs of 8 ohm speakers and a single pair of 4 ohm speakers you have to treat the 4 ohm setting as (2) 8 ohm speakers making it appear to be (5) 8 ohm speakers. So the next highest setting is Pins 5 & 6 for 8X. So based upon that if you connect all four zones with 6 ohm speakers (4) x 1.5 or (6) 8 ohm speakers so 8X would be the safe bet. But you are using higher quality components that feature High Current amplification (like our AMP200 and AMP300) which I would recommend setting the pins to 4 & 5 for 4x. Note, I believe the SSVC4 comes from the factory with the jumpers set to pins 2 & 3 for a 2X setting. You will have to remove the cover (making sure nothing is powered up maybe even disconnecting all the input and output connectors) and change all the jumpers to 4X (pins 4&5). It is also a good idea to turn off a zone using the individual zone on/off switch rather than using the volume control to turn the sound down where you can no longer hear the music.
I hope that helps
TL/3750