wattage comes in two flavors Peak-to-peek and RMS. A speaker is rated in OHMS. A 2 ohm speaker that is driven by a 50 watt amp - will be MUCH LOUDER than an 8 ohm speaker, driven by that same amp. You actually can damage a speaker with an UNDER-POWERED amp as well what happens is the AMP can't keep up with the power demand so it DUMPS all it's wattage in spurts which can damage your VOICE COIL(S). A sub-woofer is a speaker or set of speakers which has a very low FREQUENCY BAND. they often require more WATTAGE to provide the same output when compared to BASS speakers or MID-RANGE speakers. I hope that helps.
