Maybe veering OT, and I could be being OCD...but it seems to me that the crossover between mains and subs is equally as important as that between a midrange and a tweeter. It's part of overall system calibration. Boosting the sub(s) independently and arbitrarily messes up what should be a carefully calibrated crossover. Once the sub/mains crossover has been accomplished, it should be left alone until you physically move stuff around, necessitating a recalibration. Other eq can be applied subsequently, for taste, for specific recordings, for loudness compensation, or whatever other reason.