In simple terms...
You want to match the ohm (impedance) of the sub with the amp. A speakers voicecoil has a specific impedance. Most are 4 ohm or 2 ohm. Some speakers will have 2 voicecoils, those will be dual 2ohm or dual 4ohm. Regarding amps, amps will put out a different amount of power at different ohms. The lower the ohm, the more power it can put out (generally). However, amps can only be made to be stable down to a specific ohm load. Most amps are stable down to 2ohm, some 1ohm, others .5ohm. Then if you bridge the amp, sometimes it can only go as low as 4ohm. It all depends on the specific amp.
That Alpine woofer is a dual voicecoil. It has 2 voicecoils that are either 2ohm or 4ohm. THe thing to know about dual voicecoil speakers is that you have to wire the two voicecoils together before presenting it to the amp (in most cases). By wiring the two voicecoils together, you will change the impedance.
So to answer your question of what version of the subwoofer to get, you have to know what amp is going to power it. That way you can hook up the speaker to use the amp most effeciently.
Make use of the FAQ
https://www.honda-acura.net/forums/s...d.php?t=201970. Theres tons of info there.