<A name=015>Q: How much power does it take to get good bass from my sub?
A: When matching up an amplifier to a subwoofer, its important to look at continuous power. Many subwoofers and amplifiers are rated at both continuous and peak power; however, continuous power is the best indicator of what your gear can really handle. Try to match the continuous (or RMS) power rating of the sub to an amplifier with a similar continuous (or RMS) power rating. Err on the side of too much power. It is actually better (for the amp and the sub) to have too much amp and run it below its maximum output than to try and push a sub with an amp that is a little underpowered. Using an underpowered amp causes it to clip, which causes distortion that can damage your sub and amp.
<A name=025>Q: Im looking at speakers, and their efficiency ratings are only a little different. Does this rating even matter?
A: Efficiency is one of the most important specs to look at when you buy a speaker or subwoofer. You want to get the sound that you can, right? Then you want an efficient speaker. For every 3dB of difference, the amount of wattage that you need to play at the same volume doubles. For example, if all other things are equal, a subwoofer with an 89dB efficiency rating needs 200 watts of power to play at the same volume that a subwoofer with an efficiency rating of 91dB with only 100 watts going to it. By choosing an efficient sub, you squeeze every bit of bass possible from your amplifier.