Polk Audio LSi9 Dual-Driver Bookshelf Speakers (Pair, Real Cherrywood Finish) Dual drivers and the Ring Radiator Tweeter reveal pinpoint details, realistic imaging and projection, a wide soundstage with surprisingly deep and wide frequency response. The LSi Series sounds like a Polk Audio loudspeaker should: realistic, transparent, wide and embracing, with no distortion even at lifelike volume levels. Amplifier Specs:Recommended Power: 20-200 watts per channel. Rigid Cast Aluminum Driver Baskets resist flexing and "ringing" for ultra-tight bass and coloration-free midrange. The solid, non-resonant, 1.5"-thick heavy duty panels reinforce the enclosure's solid quality, helping it remain totally and more efficiently acoustically inert.