I use 90 as a bare minimum. Yes, my 17 watt triode amp has run maggies, but was lacking. Simply put, the higher the rating the better if you only have a couple of watts.
Keep this in mind:
90db at 1 watt
93db 2watts
96db 4 watts
99db 8 watts
102db 16 watts
Every time you double the wattage you will see a 3db increase. To double the volume, you need a 10db increase. So, 92db speakers should require 1/2 the power as 89db speakers. 96 db speakers(lowther) will be twice as loud as 86db speakers(maggies).
Keep this in mind:
90db at 1 watt
93db 2watts
96db 4 watts
99db 8 watts
102db 16 watts
Every time you double the wattage you will see a 3db increase. To double the volume, you need a 10db increase. So, 92db speakers should require 1/2 the power as 89db speakers. 96 db speakers(lowther) will be twice as loud as 86db speakers(maggies).