Originally Posted by YaYaDingBat
it is 4ohm and the receiver is 8ohms...I am not sure of the significance of that fact.
Ohm's law says voltage=current*resistance (=resistance to flow of electricity. Impedance is kind of like resistance except it varies with frequency a lot and other complexities). At full volume, amplifiers "clip" at a maximum voltage. The lower the impedance, the more current the speaker will try to draw.
If the amp is not beefy enough, it will get hot, possibly shut down, possibly break, possibly gush out the fires of Hell and burn down your house. OK, that last is probably not going to happen, we hope. At LESS than maximum volume, the power is less, so the current is also less, and the amp is OK.
Here are "Head_Unit’s Rules Of Protection":
1) If when things start to sound distorted or odd you TURN IT DOWN, you are unlikely to ever break anything.
2) If you constantly "turn it up to 11"
you will break something.
NOTE: the size and power ratings of the speakers and amp do not affect rules 1 and 2. (Specs for amps are often not thorough since they are measured into resistors and speakers are not resistors. Speaker specifications are 92% meaningless (and I say that as a loudspeaker engineer)).
--> Get the speakers that sound best and don't crank them into distortion.
If you decide to upgrade the amp at some point, focus on the 4 ohm power specification regardless of what speakers you will use. 4 ohm power is not a perfect measure but it's better than nothing.