Paul, good to hear from you again. What isn't clear from your description is how you actually have the bass management set up. The first point is to be sure that the connecting strips on the M80 terminals are tight so that the woofers are actually operating. Then, setting the M80s "small" with an 80Hz crossover generally works well. Although you say that you're using LFE+Main, that setting is only applicable when the M80s are set "large" and are running full-range. If that's what you meant by "also" using the "small" setting, then you're saying that you've tried it both ways, so it's understood. When using the "+" setting, if anything the tendency is for the combined bass from the M80s and sub to be excessive(assuming that the M80 woofers are working properly), so it's hard to see why the bass output wouldn't be adequate.
