What subwoofer impedance should I wire it to?

It is rated at 1 ohm, 2 ohms and 4 ohms, with output rising as impedance drops. A dual-voice-coil sub wired to 1 ohm gets the most power. Check that your sub and wiring can handle a 1-ohm load.

How much power does it make at 4 ohms?

380 watts RMS at 4 ohms, 650 watts at 2 ohms and 1000 watts at 1 ohm. Plan your sub's power handling around the impedance you actually wire.

Is Class D good for bass?

Yes. Class D amps are efficient and run cooler than Class AB designs, which suits the heavy current demands of subwoofer duty. Sound quality depends mostly on the install and tuning.

Will it work with a factory head unit?

It needs a line-level or speaker-level input signal, so a factory radio usually requires a line output converter. Confirm your head unit's outputs before installing.