Bob is right, again. I personally like subs. You can put the bass anywhere you want for the best integration and let the monitors handle the rest. It will depend on the monitor's drivers and crossover as to the quality of the midrange. Better that way than to try to make a monitor play frequencies below 60 Hz. The sub may be localizable if it plays much above 80 Hz or is too loud. I prefer a monitor that is allowed to play full range and a sub that you can change the crossover, and phase. Its your best chance to integrate it without it being noticed.
