The Polk Audio PA500.4 4-channel power amplifier packs an incredible amount of power into one single unit. Use it for 4 main speakers, a bi-amped component set, or 2 mains and a subwoofer. The choice is yours. Cast aluminum textured end caps for optimized heat dissipation and hiding of connectors. Solid aluminum logo and model panel back lit in cobalt blue. Light Bar/Fan Output-Connect an optional LED light bar or cooling fan for custom installations. Remote Subwoofer Level Adjuster included.