sure prove the rule of needing to double the power to achieve a 3dB increase. My 510's (80x2, 70x5) are just 1.25-1.5dB higher at any (usable) volume level than my 310 (60x2, 50x5). Tested 70 through 90dB for reference levels and also tested random comparable volume settings. This is gratifying to see as the 20 watt jump is only 1/3 of the 310 power rating. When I got the 310 for the upstairs system I broke it in on the main setup and found it's performance to be darn equivalent to the 510. I was beginning to worry about sub-par performance on the 5. But I've since gotten a second 510 and my tests show all is well. I'm a novice when it comes to E.E. What is an appropriate way to measure watts from a receiver? Sorry for being so anal. I love this stuff.