Those 90 pound ratings can be deceiving. That's "90 pounds pulling straight down", not "90 pounds hanging out on the end of a bracket so the resulting forces are pulling OUT of the wall".
The lower mounting point will be no problem, but the upper one will be trying to pull out of the wall, and if the distance from wall to weight is larger than the distance between mounting points you also get a multiplying effect from the leverage.
For example, 10 pounds 12 inches away from the wall, on a bracket with 3 inches between the mounting points, will be pulling OUT of the wall with more than 10 pounds of force.
I'm not worried about patching the wall; just worried about patching speakers and whatever they land on
