Is more amp power always better...?

89db speakers can use a fair amount of power. How many watts depends on the type of amp you want.  My rule of thumb is, as an echo to a few posts above, a good amp should be able to double wattage between going from 8 to 4 ohms. This helps with reserves of power for transients.  Speakers have big magnets to move. 

This applies mostly to solid state A-B amps, which is mostly what I have had.  Tube amps are a completely different conversation. 

Some manufacturers under-report 8 ohm watts per channel so that they can show it doubling at 4. But get as close as you can, as well as the sound you like. 

I’ve read that aside from the room, speakers are most important. Easier said, 90 dB  or more is the way to go. You do that & your amp choices become flexible & varied.

My CODE #16 amp has only 150 watts @ 8 Ohm and doubles 2x after that. However, it has a huge power supply and is a stronger sounding amp than amps I owned with much more watts @ 8.

An example would be the Sanders Magtech amp (also built by CODA). It has much more watts (I think 500 @ 8) but it is a weakling compared to the CODA #16. I sold the Magtech to get the $2k Schitt Wotan which at 200 watts @ 8 is also more powerful sounding than the Sanders, but not the CODA #16.

If you are thinking of going up to $8k for an amp, check out the Wotan at $2k. It sounds amazing on hard to drive Maggie’s. The Wotan needs about a month of hard break-in.