I too have used them all from QC, Crown, Lab Gruppen, Power Soft, Martin, EV, you name it I have used them and been around them. But there is still a difference between a $10k amp and a $300 amp. A touring grade amp is more then rack ears or the ability to take a beating. The tour grade amps can put out more continually, have big power supplies, better front ends, take the peaks better have better reserve power, etc etc etc.
I have been in many A/B tests and I can tell you there is a difference between amp lines and amp manufactures each one has a different tonal character to the sound and each one handles the loads differently. Can i say that you would hear that difference in a home environment? No probably not, but it is there none-the-less.