Graphic eq is prolly the best bet. I would target a pretty standard approach selecting 120 Hz as your roll off point. A classic slope is the Butterworth Thompson which is 12db per octave.
An octave is 1/2 of the freq you start from. In this case, 1/2 of 120 is 60. So, you set your curve (by adjusting the "Q" on your eq) so that you have a 12 db cut by the time it hits 60 Hz.
You can also make a few variant presets in this fashion: 9 db per octave, 6 db per octave, and 3 db per octave etc...
Try to select the harmonic points on the curve to start your rolloff. 120 and 92 are pretty typical.
As rerem points out, boomy is between 100 & 300 (and below). Many foh's push 80 - 92 to give you a real punch at the show, but without a bombin' playback system, it can be hard to replicate the rack of crown amps and a bank of 15" subs.
Rolling off at 120 preserves punch. Rolling off higher than that can take away some of the "room".
Using a high pass filter pretty much automates the above process.
Waves has a sweet analysis plug that really lets you dial in as tightly as you want to locate the trouble spots. WaveLab has a proprietary one that you access through the toolbar (can't remember how. I am at work). It does a good job, but the Waves is the $#!+.
As always, ymmv. Have fun and "save as", a/b it, and pay close attention to the settings of standard presets as a jumping off point. No sense in reinventing the wheel or curves in this case