You can try a digital crossover like the Behringer DCX2496 ($350) or the DBX Driverack ($499), which is what I have. You will be able to adjust both the high pass and low pass settings between your speakers and sub to get the best from both. You can bi-amp your speakers with another amp, if you want. Also, there is a seperate microphone available that you can use to EQ your room.
One of the problems in using just a pre with multiple outputs is that there is no crossover to stop the speakers from trying to play the lower frequencies although usually the sub has one so it will not play high freq. I learned this the hard way, I blew out a driver while playing a movie with some really loud low freq. sounds.
These digital crossovers are balanced which makes them ideal for fully balanced systems. But they can be used single ended if you get XLR to RCA adapters.
Sonny
One of the problems in using just a pre with multiple outputs is that there is no crossover to stop the speakers from trying to play the lower frequencies although usually the sub has one so it will not play high freq. I learned this the hard way, I blew out a driver while playing a movie with some really loud low freq. sounds.
These digital crossovers are balanced which makes them ideal for fully balanced systems. But they can be used single ended if you get XLR to RCA adapters.
Sonny