Wanting to mount 2 speakers to a wall. Each speaker weighs 60 lbs, we have the mounts that connect the speakers to the wall. The wall is 3 inches thick of plaster, then 2 inches of dead air space, then red solid brick. The speaker mounts have 4 holes each 3/8 diameter, 8 inches apart top to bottom and 4 inches apart from side to side. I will make steel pillars to go from the brick to the speaker mount so the weight will not push on the plaster wall, the anchor bolts will go through the pillars. Will anchors with 3/8 bolts, 4 for each speaker hold it to the wall? What kind of anchor will work best for red solid brick? Any help would be great! Thanks.