my point is, even if you get the 150wpc channel amp, you still need the 200w for the fronts to handle the peaks.
your point that the tweets and mids need only 10w is right, but then, it is when the fronts are fed bass signals that they need more power. (honestly as well, with a crossovered speaker, we really don't need that much power, it's just a man thing. but in theory, the mains will be doing most of the work which is why the biggest amp should go to them)
I agree with PENG, the surrounds will be happy dancing with 100wpc. it will always be the front LR that need the most power. next is the center.
since you have a 5.1 setup, I would now cast my vote for a front mains solution and let your receiver power the surrounds. (e.g. monoblock for the center OR a better two channel amp for the mains and move your rpa to center duty OR another rpa for the mains and either bi-amp the center or leave one channel hanging)
I've bi-amped speakers myself, believe me, it's a waste of time and effort.