Amazon.com: Audioengine S8 Powered Subwoofer Speaker - 250W 8-inch Home Subwoofer with Built-in Amplifier and Dual Audio Inputs for Home Speaker System (Black) : Electronics
AudioEngine A2+ speakers with S8 Subwoofer, and D1 24-BIT DAC/ HEADPHONE AMP | Reverb
Amazon.com: Audioengine A2+ Plus White Wireless Bluetooth Speakers and S8 Black Subwoofer Bundle : Electronics
Do I really need a subwoofer for Audioengine A2+ | Headphone Reviews and Discussion - Head-Fi.org