This one is for the guys that use a pre-amp + power-amp. I've had a question burning for a while now. I bought a new amp recently but before I parted with my hard-earned cash, I borrowed as many amps as I could get my hands on and gave them all a bit of a go at an all-day rehearsal - everything from 200w combo's right through to massive power-amps. The results with power amps were wierd. I used the same pre-amp for all of em (yamaha). The power amps were rated between 600w per side up to 1,100w per side at 4 ohms. My speakers have a total load of 4 ohms. No matter what I tried, none of the power amps would go as loud as a standard 400w head, not even the 1100w so-called-monster. I'm talking brands such as QSC, Mackie and Yorkville, all reputable. It wasn't even close. I even tried bridging to double the power and still no cigar. I ended up buying a standard 400w head and before long found myself being able to overpower PA stystems rated at 3000 and 4000 watts. I had sound engineers getting ****ty with me and insiting I turn down so they can put me back in the mix. This leads me to believe that PA power amps have a different system for rating their wattage to other musical instruments? Is this so? All thoughts welcome.