Logitech Speaker System Z623Speaker System Z623 Logitech Speaker System Z623. For big, bold, 2. 1 sound. THX Certified means quality you can count on these speakers have met strict performance standards to achieve THX certification. You'll hear and feel immersive audio from 200 watts (RMS) of power that brings music, movies, and games to life. Multiple inputs and a built in headphone jack make it easy to get great sound from up to three audio devices. Easy, two satellite setup