Amp or DAC?

will sound different - many reasons why, too many to enumerate

power ratings are very rough guides... not informative beyond 150 more than 50 more than 10 - depends on type of amp too

re- dac ... no

Absolute power is only one of the dimensions that matter: obviously, if you are trying to drive a difficult speaker load at say 80db efficiency, a lot of power is required. Conversely if you are driving 110db horn speakers a humble 2A3 valve amp pushing out 2-3 W is plenty sufficient. Generally bigger power means bigger power transformers and consequently greater emission of EMI, the shielding in other words gets more challenging. 
Where it really gets interesting: a clean renderer and DAC, i.e. units with a very low noise floor can increase the perceived loudness. Since the amp has to amplify only clean signal rather than a lot of grunge on top, the perceived result appears louder. NB: there is no increase in power, just perception.

I have no idea what you’re running but a well implemented purifi or Ncore class D amps will better most AB amps in noise except the Benchmark AHB2. Your DAC, even ones that don’t measure state of the art should have less noise than good SS amps. I wouldn’t worry about the watts to much unless your speakers need more power. I have 500w class D doing bass and 2x250 W class D on mid and tweeter in an active speaker and I never have any problem with noise.

@djones51 it was a Purifi compared to a Hegel H90. Great clarity/quickness with the Purifi, but didn’t notice any more ‘control’ of the woofers from one vs the other. 
Have you compared an AHB2 with your class D amps? 

No never had the Benchmark amp. Not sure what you mean by control of the woofers, what speakers.