I always "overdo" the sizing of the amplifiers simply because more powerful amps don't have to work that hard to produce a lower output, so as Steve said you don't get any clipping.
High frequencies don't need a whole lot of power to be loud, because the speaker cones (usually domes) in tweeters are small and there isn't a lot of mass to move.
Woofers are different because the voice coils and speaker cones actually have some serious mass to them, which is what helps them move at lower frequencies as well as "move air".
Venture into a techno, house, dance type nightclub and often you can feel your internal organs sloshing with the beat. This is because the club has 1000W amps feeding their 18" subs
In a recording studio, loud is not the most important charactoristic of your monitoring system, but rather accuracy... meaning the speakers are faithfully reproducing what you've recorded as exactly as they can.
A hard limiter is a good tool, because its silent and "uninvolved" until something goes wrong, then it vastly compresses the signal to the amp to avoid clipping and overdriving it. Also, fuse your monitors. The monitors I use have a seperate fuse for each driver, at different ratings for each driver. Just in case the crossovers decide to short.
And Rick, there is nothing wrong with a 350 for casual driving - I'm just about the bolt the heads on a 502cid stroker ford engine for my truck. Then, I'll be welding to the exhaust manifolds so I can attach two turbos. The truck is my daily driver and I mostly drive this crew cab unloaded, so this is gross overkill. But the one day when I attach the trailer or load up the bed with patio bricks, its nice to hit a hill and not notice it, other than the coffee sloshes to the backside of the cup
heh-heh