[tom406]

How are they wired? If they're wired in series (non stereo) for an 8 ohm load, they'd be just fine if there's a second set of outputs. Basically, its my understanding that whenever you drop the resistance (ohms) by half, the current the amplifier tries to deliver is doubled, and these high currents are what get you in trouble. I'm not familiar with what the factory did when you got the optional rear speaker on some of these setups. I would look at the factory wiring diagram, and just try to keep the ohm loads withing at least 60 or 70% of what the original setups were, and then avoid cranking it up excessively.