How badly did the 4 ohm JL's affect the volume output of the Shaker system compared to the 2 ohm factory speakers? I know that it takes a 10x increase in amplifier power to double the volume, but it still seems to me that cutting the amps output in half would not be a good thing.
I can't answer that question because I installed a 4 channel amp to run my JL door and rear deck speakers. However, I did keep the factory door subs running on the factory amp. I heard that Infinity was the only company offering a 2 ohm replacement speaker. Not sure which model though.