You actually boost and cut by 20dB?! Ouch. In most applications, I don't think you'll be hearing much difference after boosting frequencies more than 10dB or so, and you'll be requiring your playback system to provide a tremendous boost in power, since theoretically, every 3dB of boost requires twice as much amplificatoin power, especially in the low end...so you could either get some distortion or every other frequency will suddenly be robbed of power. Whatever you boosted by 20dB, try taking that down to +6dB and see how much difference you hear. Anything past that, and you'll likely be trying to boost frequencies that just aren't there to begin with (as is usually the case when the raw recording is lacking in any area). Also, depending on the fidelity of your editing sound system, you could be doing things to the sound that you can't quite hear now, but will become evident when played back on a bigger system with a subwoofer and what not. Suddenly there might be a disturbing rumble to everything, and you could also risk damage to amplifiers when the reference is set to things that didn't need boosting.
So as a quick fix for bringing up some more low end in a musical live performance, you could add some boost to things, say lower than 180Hz, but don't just spike it and let it go. Try some lower settings and listen on different systems if you get a chance. Little desktop speakers and most TV speakers won't give you anything under 120Hz or so, so you won't be able to tell if there's anything there or not. Boom boxes usually create a simulation by bloating up the lower-mids, so that's not accurate either.
If you have some time later on, you should move the recording into a studio or recording facility and have the bassist overdub some of the lines if need be, etc. Lots of professional 'Live' releases do this. But anyway, good luck, and be careful how much you boost that low end.
