Hi, Tireguy, there is a guideline for power:
the efficiency of your speaker is 87 db means with
1 watt input, they will produce 87 db sound if you
measure sound pressure on axis, 1 meter away from
your speakers. If you want to increase 3 db, you
need to double the power of your amp. For example,
you need 2 watts to get 90db, 4 watts to get 93db
and so on.
I hope this will help you a little.