Mike is certainly right about the specs on the SRM450's. Mackie doesn't claim these are 450 watt speakers, although some may think that based on the model number. And they are indeed bi-amped, which allows them to use an active cross-over network.

In designing an integrated amp/speaker package such as the 450's, you'd better believe that the amps and speakers are matched for best overall performance. They've got a limited volume, a limited ability to dissipate heat and they've got to strive for the best overall performance given all the variables they have to work with and the design compromises that have to be made. And based on what I've heard and what others have said about the Mackies, I think they've done a darn good job.
Paul C.