Why don't you use an SPL (Sound Pressure Level) meter?

[sygyzy]

I believe most people here know about SPL meters, have them, and use them. I always level match when comparing speakers and usually do it with amps too.

Also, I think most know to recalibrate their system after changing any componets.

I think this reply says it all. It's like asking "Food is important, why don't people eat it?" Answer: they do.