I did clock you really liking the result of boosting the bass EQ whilst engaging the HPF on your Mesa D800+ a while back. And this seems, from the discussion above, to be a really good "take-away" point. If I recall correctly (without RTFM at this time of the morning when I should be working 😁) the Mesa bass EQ is centred at 80 Hz? Out of interest, how much were you dialling up the bass EQ by?