300 Watt MOSFET Amplifier
^ Yep that means it has an amp!
It's the way the amp works, class D tends to use around half the power of a normal class AB amp, but it does have a few drawbacks also, but for sub use that doesn't really matter. I haven't a clue how well made the speaker and box is tho but I'm surprised to see Class D being used here as normally Class D amps are pretty pricey...