I know I am still Rip Van Winkle in the brave new world of audio, but three points come to mind about powered speakers that militate against them for me:
1. What if the amp function within of of the speakers breaks or just stops working after a long time, and the manufacturer is out of business or more likely say they "can't support" the old version of the amp because it is too old?
2. What if you like to modify or adapt the sound of your system to get it warmer or brighter or something? I assume there is nothing you can do with powered speakers. (The only ones I've heard-- except audioengines-- have sounded ok, good, clean, bright, aggressive and anonymous.)
3. What if you want to try tubes or use your older amp that's still good but you don't have other speakers. Out of luck, right?
I may be wrong about these, but thought I would bring up these considerations that hold me back.
1.) Nearly the same argument for integrating any two or more functions into one cabinet. It's a gamble to save now and possibly pay later or just pay more up front. But integration has it's own benefits (saves space, cables, manufacturer picks synergistic matches - assuming you trust the manufacturer enough to buy his gear to start with).
2.) Most cheaper active monitors (under say $500 each or found at Guitar Center) do sound as you described, but when compared to similarly priced passive speakers (when taking the cost of amplification into account) beat the pants off them. Expensive passive speakers sound dull, bloated, colored, and lack detail compared to quality active monitors. Active studio monitors are workhorses, meant to dig into the truth versus home passive speakers that are meant to tickle particular fancies. The question is, are you ready for the truth or do you want to chase your tail to satisfy what entertains you?
3.) Bryston has a solution for those who want active and yet pick their own amps, but it's bulky, complex, very expensive, and could sound like crap when you're done inventing your own recipe.
And besides, active have many sonic advantages, some of which I spelled out above, that make passive obsolete.