I'm confused about some of the terms that I often read in the specs of speakers: - Freq: 35-20KHz at ± 3dB (what's the ± 3db for?) - Impedence: 8 ohm (why should I care about this?) - Lower Freq Extension: 30Hz (DIN) (what's that exactly? What does extension mean?) - Sensitivity-Room/Anechoic: 91dB/88dB (what's the difference between both numbers? What should I care for more?) - Suitable Amplifier Power Range: 15 - 350 watts (???) - Maximum Input Power: 210 watts (???) I would really appreciate your feedback guys.