A pre-amp with 2 pre outs will let you run one set direct to the sub and the other set direct to the mono amps or stereo amp. The amp/amps will be getting the full range of the signal.
Some subs will divide the signal into low for the sub and then have a pre out with the remaining signal to feed the amps. Your sub may do this now? This is a good set up if you have speakers with not much bass. It will protect them from damage.
Some subs will divide the signal into low for the sub and then have a pre out with the remaining signal to feed the amps. Your sub may do this now? This is a good set up if you have speakers with not much bass. It will protect them from damage.