I am planning on building a home subwoofer using the plans outlined on Adireaudio.com for the Tempest and 2 of their PR15 Passive Radiators. What I am wondering is would it be better to use the plans to use ports or to use the passive radiators? I want the sound to be flat down to somewhere between 15-20Hz. What am I better off doing? I don't care that the PR's cost more than the ports.