I don't think so. Unless you have a rather large listening room, you listen at very high sound pressure levels and have your listening position over 15 feet from the front speakers, you rather need one or two better subwoofers for better bass. The SR7012 has a rather flat frequency response over the full audible range. In addition, the other Kliipsch speakers are adequate and don't demand that much power taking into account their sensitivity.
Many threads run on this site on subwoofers and you should definitely find a suitable answer in a few of them.