Do I need a separate amplifier for these enclosures?

No. Each enclosure has a built-in amplifier, so you only need to supply power, ground and an audio signal from your head unit.

How much bass do two 8-inch loaded subs produce?

Enough to fill a car cabin with added low end, but each is rated 240W max. Expect a solid daily-driver upgrade rather than competition-level output.

Will these fit in a small trunk?

The 8-inch driver and prebuilt box keep each enclosure compact, which suits hatchbacks and small trunks. Measure your cargo area before buying two boxes.

Can I use just one enclosure instead of both?

Yes. Each enclosure is self-contained, so you can install one and keep the other as a spare or for a second vehicle.

Are these safe for a boat?

No. They are not rated for marine use, so keep them in a car or other dry, enclosed space.

What do I need to install them?

A power wire with fuse, a ground connection, and a signal feed from your head unit or line output converter. No separate amp or box build is required.