Is more amp power always better...?

I have a pair of very efficient speakers at 12 ohms impedance playing in a modest listening space and the best sounding amps are those of low wattage class-A.  I've heard a number of class-A and class-A/B on my speakers, even those of class-A/B with the first several watts in class-A.  With really good and well-designed class-A/B amps, usually their first several watts are class-A and for many speakers at moderate volumes don't exceed much past class-A..  I have two First-Watt class-A amps (10 - 20 WPC) that are quite articulate and have plenty of power to handle my listening levels.  That said, you will need more power than those can deliver for your 89-db speakers especially at higher volumes.  Also, it depends on how well the amp can supply current if the impedance is low.  If your speakers are a true 89-db, they are playing at 89-db with 1 watt of power at about a meter from the drivers.  That level goes down about 7db at the listening position to about 82-db.  When I'm listening, most times, I like listening between 85-db and 95-db.  Any higher in my listening space and everything starts to get jumbled up sonically.  Looking in your case at going from 82-db to say 95-db at your listening position, you have to have enough power to drive the speakers to that level and higher on peaks.  Thats a 13db listening range.  With your speakers 82-db at the listening space is 1-watt of power and at 94-db would be 16-watts.  I have read that to be safe, you should have enough power to drive ~10-db above your normal listening levels for peaks.  That would equate to about 128-watts of power/channel.  Let me preface this with some caveats...  That assumes you have speakers that are 89-db and generally run no less than 4-ohms minimum impedance.  You'd need an amp that can deliver a good, clean 128-wpc into an 8 or 4 ohm load.  If your speakers dip notably below 4-ohms, you'd have to make sure the amp can deliver enough current to get to the 128 WPC.  Please note that my information above is based on a number of assumptions.  I personally don't need much power as my speakers are 106-db efficient so are operating most of the time in 1-watt or less of power !  I can get away with flea-watt amps easily.  Good Luck on your amplifier search !