I find that monitoring on a flat response, and then boosted response works wonders, because then you see what might be exaggerated in the mix, especially what might be too boomy, or not full enough. I find that it's then good to have a balance between the two, between the flat and the boosted response...in the boosted response, I usually put the bass to about the 2 to three o'clock range on the knob.
I don't advocate making either your flat or your boosted mixes your main weapon, rather to toggle between the two to find a happy medium. For most stereos that I listen to the mixes back on, I find that anything above the 3 o'clock range on the knob generally tends to be much too muddy on any speakers. It's kind of a bonus and a drawback that there's treble, bass and sometimes midrange knobs, as well as equalization on stereos....because sometimes people turn them all the way up, which ruins the balance and care that the mastering and mixing engineers put into the recording. I also think that there's a misguided belief that listeners think that because they have an "XBS", "SuperBass" or whatever function on their stereo, that they need to have that stuff on.