the right box size
I've spent the better part of the day searching the forums (very active) for info on a box my gnx104 sub. i bought it at frys about a year and a half ago for $30. I have a volvo 240 and plan to mount it coming through behind the rear head rests. Space is not a concern (to a point). I see some people saying it should have a volume of 1' cubic feet, and others including the plans on the polk website for .65 im more interested in fidelity over shaking both me and my car.
also anyone think that the Hifonics ZXi 8006 is a suitable match? the subs rms is 175 the sub output on the amp is 200 rms.
I would follow what is stated as the correct volume on Polk's website. You could build the box and if you do not like the sound, increase the box size a little to get more low end extension. My subwoofer calls for .90 cubic feet, and I am running it at a little over a cubic foot after taking the driver's displacement into account.
You should be fine with that amplifier. My sub is rated for 350 watts RMS. My subwoofer amplifier is putting out 398 watts RMS. Just set the gains properly.