There is no standard for assigning a "200W" rating to a speaker (often assigned by the marketing department), therefore we don't really know what a spec sheet means when they assign a "200W" number to a speaker. I don't want to drop B&W into this bin, but low quality manufacturers tend to assign a high number to attract unsophisticated customers who might assume that a bigger number implies a better speaker. And, attaching a 100W amplifier to a 200W speaker is no guarantee that the user cannot damage the speaker.
I am a fan of bi-amp when an active crossover is inserted ahead of the amplifiers. This is difficult or impossible to accomplish with an AVR --- and this will require an additional "box". Many AVR's offer a "bi-amp" mode, but this does not insert a crossover.
---
At an elementary level "harmonic distortion" means that a device adds components that are integer multiples of the fundamental frequency. If one inputs a 1KHz signal, the output will be 1000, 2000, 3000, etc. The magnitude of the "distortion" is expressed as a ratio of the harmonics and the fundamental. Lower harmonic energy is more desirable.
There is also "intermodulation distortion". Here, sums and differences are added by the device. If we input 100Hz and 1000Hz, intermodulation products will be produced at 1100Hz and 900Hz.
If you push these concepts through a real world amplifier, both types of distortion are present and as we input two simple tones, a blizzard of products emerge because there will be harmonic and intermodulation distortion of the of the distortion products. Above, there will be additional distortion components at 1800Hz and 2200Hz, and 1800 +/- 100 --- etc.
Of course, better quality amplifiers (and speakers) will minimize the production of spurious products. In the bi-amp arrangement that inserts a crossover ahead of the power amplifiers, each amplifier is given a simpler job because of the band limited input. Harmonic distortion is tolerated well by humans, intermodulation distortion is annoying.
---
As others have commented, room considerations often swamp equipment considerations. Simply rearranging the placement of speakers in the room can have a big payoff for no additional expense.
