The SQ is essentially a DD 95 knockoff. It is designed around the box. The "DD Box" to be specific. Use the sizes/ratios on the DD website and you should do well. All reports suggest that that sub likes large-ish box tuned high with large port area. It will be sub-optimum for movies but it is a good tuning for music.
Keep in mind if you lurk the HT forums people test sub-stage with certain movies that have sound effects (explosions, helicopters, or the dinosaur footsteps in Jurrassic Park) that extend down well below 20hz for reference material. The HDC3 is really not designed to do that, but on the bright side if you're using typical 200-600W size plate amp on it, it will have enough x-max and a tight suspension to prevent you from breaking it when that material comes up in movies.
Alternately, if space isn't an issue you may well be able to use an "ABC Box" to tune at 25 and 50hz which would pick up both sound effects and also have that punch you'll want for your 97.9FM type music (I assume you're talking about the kind of stuff they play on that station in NYC?)