Yes. TYPICALLY watts == sound levels. but some speakers are more efficient than others - this is expressed in the sound pressure - typically measured in dB for 1 watt at 1 meter. If you're comparing the ratings for different speakers, 1 dB is hardly audible, 3 dB is definately audible and 10 dB is a big difference. Ohms measure the impedance of the speaker - the resistance to electricity passing through it. The speaker impedance should match the amp's load requirements. An amp rated for (say) 200W into 4 ohms is designed to work with 4 ohm speakers, but will also work just fine into 8 ohm speakers, but at reduced power. On paper, you should get about 100 watts into 8 ohm speakers but it varies. If your amp is rated for 8 ohm speakers, and does not specify 4 ohms, you should not use 4 ohm speakers. It can destroy the power stages of the amp. You can double up speakers. If you connect two 8 ohm speakers in parallel, meaning connect both red terminals together, and both black, and then connect to amplifier, the pair of 8 ohm speakers functions as one 4 ohm speaker. Some amps are designed to handle a 2 ohm load - two 4 ohm speakers in parallel is two ohms.

You need to check the total rms output. The higher the total rms the better the speakers. You can have speakers with a 100 watt output with a low rms and the sound quality and performance won't be too good.

yeah...n38 hit the Ohm's law and tech explanation accurately enough. Real world: higher wattage rating has NO bearing on what volume you will hear on a given system. If your stereo is pumping out 27 watts, it won't make any difference if they're heard on 50w or 500w speakers. They'd blow up if you cranked 27 watts into 2 watt speakers tho. Match your speakers to more than your amp puts out, and match it's Ohm ratings. Bear in mind that lots of places "cheat"....like Pyramid car audio junk...They may boast about an "800 watt power amp" that puts out 200 watts times 4 channels...peak to peak rating into 2 ohms...so that's arguably an "honest" 100 watts per channel...but at 2 ohms...so it you send the same output to an 8 ohm speaker, you'll hear an effective honest 25 watts in any given speaker of your badass 800 watt amp. Yawn.