The first watt is all that matters. If the first watt sucks, it the next 599 don't matter.
My speakers are "rated" at 800 wpc. that is the max you can put into them without blowing something. That would be good if I was using them for a PA system at a football stadium. I'm driving them with a 2 wpc SET.
My speakers are more sensitive than yours so you'll need more wattage. At 91 dB you're likely limited to SS amps but some will argue that.
Buy the best quality amp you can afford. You'll need 100 watts unless you are planning to damage your ears and exit the hobby as quickly as you entered it.
Most of the time you'll be listening to 1 watt or less.
So I'd say don't buy an amp that spent money to make 600 watts, but one that got the first watt right.
Jerry