I totally agree.
I look at it this way, if you want to get the most out of the speakers, you should have the max power on tap, or close to it. 1500 watts would be nice even if you don't use it all. Trying to push them hard at a quarter or even half power is not going to sound nearly as good.
Like Massive said, if you're not interested in max volume (or even close to it) you can get by fine with low power, but most of the time people just keep turning it up more and more, and you end up with supremely shitty sound.
If you try to use them with low power, and you notice that they start to sound shitty at higher volumes, or they break up or distort, just remember that it's not necessarily the speaker's fault. You just need to put more power to them.
My old band lugged around some 2000 watt peavey cabinets for a while with about 500 watts hitting each one. It could get pretty loud, but was severely limited. When I finally convinced the band to pony up for some big power, it was like getting new speakers too. It's worth it.