Too Much Power

are the drawbacks to that much power?

Size, weight, heat, and if the gain values are high perhaps a little noise but quality amps are very quiet today. 

Thanks. But as the 1200's are class D amps, size, weight, and heat would not be a concern.

I was answering what sounded like a more general question. 

Overkill in some cases perhaps but with modern amp technology no real downside, all else held constant, at least these days. It’s like an oversized engine in a car. Worst case you are paying for an insurance policy. In years past, extreme size, heat and weight were common downsides.

Too much class A power creates unnecessary heat.  In a class D amp (or generally class AB) there is no real practical drawback. 

You might find that an amp that is designed to put out 600 wpc didn't focus its design on making the first 5 watts (where you will be listening the most) the best that they can be.  I currently use a 6 wpc amp, just for that reason.