Thats the thing I dislike most about BB/CC. The same guy that is trying to troubleshoot your car can be found the next week trying to sell you a microwave and all of a sudden hes a pro at them too.
Out of phase means you have two speakers playing opposite of one another. Our ears interpet sound by vibrating air waves (compression and vacuum for lack of a better term at 5:00 in the morning). When sitting in the drivers seat, and the left & right speakers move in at the same time, they are considered to be "in phase". If you have one speaker that moves in while the other moves away from you, they are "out of phase". In the car enviroment out of phase (with the midrange speakers only) is not necessarily a bad thing. Most cars are set up terrible for GOOD sound quality. You are sitting 2 feet from the drivers side speaker and 6 feet from the passenger side one. By the time the compression part of the driver's side sound wave hits your ear, there is a slight delay for the passenger side to hit your right ear. Sometimes you can overcome this by purposely putting the drivers speaker out of phase. Some cars sound better this way. My car doesnt because the 5.25"ers are down in the kickpanel, which puts the distance further away from your ears (5 feet drivers and 7 feet passenger) which is slightly better for the sound to hit both of your ears at the same time.
An amplifier doesnt care if your speakers are out of phase, it may or may not sound as good, but it doesnt care. An amp cutting off (whether it be headunit power or an amp), usually is doing what I described up a couple threads.
Sorry for the long post, but after 16+ years at a car audio shop, the "big box" stores really tweak a nerve with me. Yeah you might find one guy every once in a while that knows his stuff, but that isnt the norm. They are salesmen first, knowledgeable beyond their own personal car, dead last.
-There are 10 kinds of people. Those who understand binary, and those who do not.
-If we ever forget that we are One Nation Under God, then we will be a nation gone under...Ronald Reagan