Is the DMD500.1D powerful enough for one subwoofer?

Yes. It is a monoblock rated at 500 watts RMS, which suits a single subwoofer in a typical car system. Match the subwoofer's RMS rating to the amp's output at your impedance.

Can I use this amplifier in a boat?

No. It is not rated for marine use. Salt, spray and constant moisture will shorten its life. Choose a marine-rated amplifier for a boat.

What impedance does it run at?

It is a monoblock Class D amp designed to run at low impedance, down to 1 ohm. Check the exact rating for your subwoofer's voice coil configuration before wiring.

Does it come with a remote bass knob?

A bass knob is not part of the core package. Confirm with the seller what is included before you buy if remote level control matters to you.

How does it compare with a Class AB monoblock?

The Class D design is smaller, cooler and more efficient. A Class AB amp of similar power is larger and runs hotter, but some listeners prefer its sound.

What wiring do I need for it?

Use an adequate-gauge power and ground cable for the current draw, a fuse near the battery, and a good ground point. Thin or poorly grounded wiring will limit output.