I usually use quality sub with monitors. The proper crossover freq really is one time setting that won't need to change once set, but the volume level of sub I do change slightly depending what music I play. Rock music which usually has pumped up bass anyway gets lower setting and classical music gets higher setting..........I find this a very useful/flexible feature of monitor/sub speaker set-ups.
With large full range speaker you are locked into single bass level response which sometimes is not ideal balance and can overpower the midrange for instance.
With large full range speaker you are locked into single bass level response which sometimes is not ideal balance and can overpower the midrange for instance.