My apologies for bumping an old thread here, but I wanted to give a quick update on this.
After my initial PS312BK, 2 different BIC PL-200s, an SVS PC12-NSD, I finally went back and purchased ANOTHER PS312BK. Out of all those subs, the Infinity clearly has the best sound quality and low frequency extension in my particular setup.
This one doesn't seem to rattle. Maybe the first one was defective or something. I retract any previous statements about the Infinity Primus lineup being poor. I'm really enjoying my Primus mains and PS312BK sub now that I have them dialed in with some good hours on them.