I'm running a GK 400 rb iv rated for a minimum of 4ohms. I don't want to do anything that would damage my head. I have been running a 210 cabinet with two 16 ohm speakers in it wired in series. I want to add a 4ohm cabinet to the mix. If I'm running the two cabinets out of the parallel outputs of my head what will my impedance be? I know this is kind of a mess, but I can't afford to buy new cabinets so I use whatever I have on hand and this is all I have right now.