The db scale is log. So your receiver would have to produce 10 times the power to get the same loudness with the 88 db sensitivity speakers as the 90 db sensitivity speakers.
Most decent speakers though are in that 88/89 db sensitivity range.
First, double checking, did you mean 98 db speakers, not 90?
Does anything bad happen if I am pumping 10 times more power through receiver? I ran two power lines to my entertainment center, the first for the TV, Roku, blue ray, ethernet switch, and receiver, and the second separate one for a subwoofer (which after 9 years I got a subwoofer that needs its own circuit). I am not overloading the circuit.
I'm looking at the math. Several websites say doubling the distance drops decibels by 6. So 1 watt will produce 79 db where I sit. 10 watts 89 db, 100 watts 99db. So if I listening to a movie at 80 db, and jet flies over and it jumps up to 100 watts per channel. Is that bad?