Putting peaks in a speaker's response is a valid approach under the right circumstances. A really good example is putting a 3dB hump on the bottom end of an HT satellite to do the baffle step compensation. However, in your case putting a hump in you speaker to take care of a room mode doesn't sound like a good idea. Once you get Qtc above 1 as you will in this case, transient response is going to suffer due to ringing. You would be much better off to find th source of the suckout and try to fix it.

Bob