Jack,
First, welcome to the Forum!
AudioControl makes excellent equalizers (the only consumer brand worth considering, IMO). However, as much as I love those German names I believe the Richter only has ½ octave resolution. Most of the time this will not give enough adjustment options. Most of us here use 1/3 octave or parametric EQs for our subs. You can probably get a decent parametric used for less than the Richter costs.
The best thing to do is take some readings (at least 1/6 octave) and post them here. Who knows? If your response dips or peaks are broad and happen to center the same place the Richter has a band, it would be a good choice.
Regards,
Wayne A. Pflughaupt