Is more amp power always better...?

The simple answer is rarely.  If  you want to seperate  out the real garbage  form the better quality  from a piece  of paper is look on the spec sheet  at the weight.  A friend  years  ago bought a 5x100 watt Sony home theater  receiver  it weight  was less than 5 pounds  it was a gutless horrible thing.  He then got given  to him a old pioneer  receiver  that was 50 watts x 2 and he got something  that had some guts a real power that didn't  blow up all the time it's weight  was around 40 pounds. Better sound. That is a very simple way to make the first cut before  you listen  but if they weight  something  it will be better than a item  that the box and packaging  weights  more than what is inside. A quick way to judge low-fi

I'd say almost always, but too much in excess of necessary may not be needed. 

200-300 watts. For example: MC312

this is one of those "all things being equal" situations. where yes, more power is always better if the amps are otherwise equal. the reason for that is that amps sound better when they have headroom, meaning they are operating in their lowest stress point and lowest distortion point, which allows them to give the music ease and authority.

OTOH it’s rare that all things are, in fact, equal, between two different amps. some less powerful amps have simpler, more musical and refined sound than more powerful amps do for various reasons. so even though an amp might have an easier time with some speakers in some rooms, you cannot paint with a broad brush since amps circuits vary.

there are some obvious amp <-> speaker pairings in large rooms that are not going to work very well. so sometimes you really do need that more powerful amp. but your goal should be the right amp, not necessarily the most powerful.

one other important factor regarding amplifier and speaker matching for a particular room is the type of music you want to hear. if you want 'large scale' and 'very dynamic, complex' music to sound natural and not limited then more power is more significant. if you like small combo or girl with guitar mostly then amp headroom is not as important. if then later your tastes change then the system capabilities might need to change with it and you may need a more powerful amp, or an easier to drive speaker system.

IMO, Amp / speaker pairing is a tough nut to crack. So much comes into play. Listening preferences I think is a major factor that gets overlooked. I’ve had a 200wpc beast that didn’t sound good unless it was pushed to volume levels I don’t find enjoyable. Whereas on the other hand I’ve had 75wpc do the job rather well. Definitely do as much listening as possible before pulling the trigger. Good luck!