Well, you'd need 2 200s if you wanted to drive both fronts (left & right.) If you were to add more beyond that, a third to drive the center would probably make the most sense. That's what I did.

External amps for your mains would in effect give you "separates" for 2-channel stereo, but if you rarely listen to 2-channel stereo this might not matter to you.
The impact of more power for the front channels only on movies is more subtle in my experience.