John, looking at those numbers it doesn't appear that room modes would explain the peaks which you measured. Assuming that the measurements were accurate(did you actually hear the peaks at those frequencies?), it possibly could be related to boundary reinforcement(which is entirely separate from room modes)at those frequencies. The sound bouncing off the nearest room surfaces(floor and two walls)reflects back to the woofer cones and can either increase or partially cancel output at frequencies related to the distances of the cones to those boundaries. For this reason the distance of the woofer cones to the floor and two walls shouldn't be nearly identical, but rather as dissimilar as possible, so that the boundary peaks and valleys don't pile up at the same frequency. Maybe this isn't the factor involved, but you could temporarily move the speakers to appropriate distances to see if the peaks are smoothed out.
