Is more amp power always better...?

Definitely not always.  We also can't really say this is true about having more damping factor. 

The amp/speaker match up is important as is the quality of the first few watts of power.   There are definitely speakers with troublesome impedance curves that like big amps with low output impedance, but also large speakers with big woofers that can benefit from high output impedance.  See Nelson Pass's writing for the latter.

If you want to see  the impedance curve you can use Room EQ Wizard with a home built wiring jig to measure it, or you can buy Dayton Audio DATS (what I use) to chart it.