I use the 402 with a pair of B&W CDM 9 NT (a couple models below the 803 but with the same recommneded power) that has a sensitivity rating of 89 db/w. There is no reason why you would be using all 400 watts of the 402 unless you are seated 35 feet away from your speakers :). I find the 8 ohm tap sounds best for my system. You can't go wrong with either amp as both have plenty of power, but you needn't be concerned about damaging the 803s with the 402. There is a power meter on the Mac (as you are aware) which I'm sure is only somewhat accurate. However, for the loudest SPLs I can tolerate, the amp has never been pushed above 100 watts.