While I can't totally agree with Ciaonozo that subs playing to 100hz is retarded, his sentiments on bass boost are still more or less correct at least in terms of using it as an equalizer. However, the issue with bass boost, IMO, is that is only boosts, can't cut and is centered at 45hz. In my many years of car audio, I've never seen a car need help at 45hz, ever. 40-50 is where most cars have major peaks at so they are already too loud right there, in most of my installs I end up having to cut that region not boost it. So from a practicality standpoint, bass boost is stupid as it will hardly ever be used by anyone smart enough to know how to use it, as it's not necessary.
However, his points on EQ'ing are more than fair. Your first goal should be to get a balanced sound, then turn it up until your weakest link comes into play, usually wherever you had to boost, but not always, impedence plays a role here too. Lastly, even a split second of clipping at given frequency tends to sound better than having a major dip in frequency response. I'd rather clip my amp by a few db's and have a flat response at say 60hz than simply let it dip off and lose the punch on drums that I like. Granted, its' best to mess with other things first, box orientation, box design, etc, but last resort, a few db of boost in the right areas go a long way and sometimes cutting everything around it just isn't a good option.