Thanks so much again, RD and Seriously. Took all suggestions onboard, and re-ran RP.
I now have bass sounding like it's coming direct from the LCR and not from the garden. Tight, fast bass which isn't hanging in the air like it was. Plus, I'm not getting nasty room modes anymore.
Not sure if it was the 68cm M&K distance add-on, the LFE internal MP-50 crossover hike or the THX Bass EQ. Probably a combination. Hardly matters, all sounds wonderful now. Sublime actually.
Right on fam.