given that you are considering a decent amp, and not one from walmart--
My advice is that if your speakers have only one set of terminals on the back to go with the 200w amp instead of the 2x100w. you have a greater chance of degrading the signal or introducing a problem than to recieve benefit. if your speakers have two sets of terminals (that are bridged, you remove the bridge when you bi-wire/biamp) then two amps would increase your chances for a non-negative result. giving you greater control over how much amp goes to the highs and what goes to the lows... Don't forget that many amps are bridgable, so you could wire two 100w amp channels to the same speaker to get 200w that way too.
My advice is that if your speakers have only one set of terminals on the back to go with the 200w amp instead of the 2x100w. you have a greater chance of degrading the signal or introducing a problem than to recieve benefit. if your speakers have two sets of terminals (that are bridged, you remove the bridge when you bi-wire/biamp) then two amps would increase your chances for a non-negative result. giving you greater control over how much amp goes to the highs and what goes to the lows... Don't forget that many amps are bridgable, so you could wire two 100w amp channels to the same speaker to get 200w that way too.