The amplifier is built into the speakers and this is the spec of the unit. Power Output: Total system Power 150 w Stereo Power (¿) 20 w x2 (8) FTC THD 0.8% Bandwidth 200 -- 20,000 Hz Surround Power 20 w x5 (8) Bandwidth 1 kHz Subwoofer (¿) 50 w (8), 20 -- 200 Hz, @ 0.8% THD Built-in Amplifier (channels) 6 Audio Inputs 3 Dolby Digital 5.1 Channel Input To reproduce stunning surround sound, the speakers accept 5.1-channel audio inputs from the supplied DVD/CD Player. Dolby Pro Logic The classic system that brings home the excitement and emotional impact of movie sound tracks. Dolby Pro Logic sound tracks are encoded in many VHS Hi-Fi movies, TV dramas and sports broadcasts. This is a four-channel system, requiring Left, Right, Center and Surround speakers. Advanced Super Acoustically-Loaded Woofer (SAW) Higher efficiency, higher output and more impactful bass are the benefits of Sony's newly refined SAW design, incorporated in the SA-VA700 and SA-VA500. Subwoofer Mode 1/2/Off Auto Power Input TV Only Bass and Treble Controls Enable you to adjust tonal quality. Remote Commander Unified TV/Video/DVD/CD Control YES(on RC) Surround Modes 5 Center Channel Modes Normal, Wide, Phantom and 3-Channel Logic modes adjust the Pro Logic circuitry to your needs. Center Channel Output Suitable for connecting external, center-channel speaker to the SA-VA100. It enables future system expansion. Rear Surround sound Wired Wireless Rear Speaker Port Lets you connect the optional SA-IF70 Wireless Surround Speaker Package. This eliminates the need to run speaker cables from the front to the back of a room. Level Adjust Center, Rear. Subwoofer Delay Time YES (3 step) Muting On Remote This switch lets you silence the speakers for temporary interruptions, like phone calls, then immediately return to your former volume setting. Display Dimmer On Remote Speaker Unit FRONT: 4", Mid/High CENTER: 3 1/4" x 2 REAR: 3 1/4" SUB WOOFER: 6 1/2"