I think the device your looking for is a leveller. I have a Aphex Compellor in front of Stereotool instead of the built-in AGC and it's keeping all frequencies at roughly the same level. In my opinion the Compellor does little to nothing in coloring the sound.
I have not read all the comments so this may be already suggested.
Well guys, the very first thing I noticed was quality loss in the bass which was dull and flat. When I switched back from Breakaway Pipeline to the pc's speakers the difference was as clear as night and day.
The Multiband works to some extent, I have some tunes with very heavy bass and the software was not able to normalize it.
I would appreciate very much if I can link you guys to one of the tunes on my google drive. If you can play it with and without your frequency leveler and tell me what happens will be nice?