Pretty much any floor-standing speaker whose woofers are driven by dedicated amplifiers built right into each cabinet.
Power towers are now available from numerous brands in a wide range of prices and sizes.
Definitive is offering it both in stereo pairs and as part of a ProCinema 400 home theater suite that includes the ProCenter C2 center speaker and a pair of conventional two-way bookshelf models, either the ProMonitor 100 or 200, for the surround channels. The ProTower 400 has a stylish shape, with a smoothly curved back and sides that flow seamlessly into the front baffle. The grille frame is also rounded, leaving the bias-cut top panel and the bottom as the only flat surfaces. Unlike wood, PolyStone can be easily molded into complex shapes and engineered toward a desired density to reduce resonance. The ProTower 400 has binding posts for a speaker-level input from a receiver or amp.