I haven't owned the ultra XL, but I have the ultra lead with a mod and that is the most gain of all the modules I have owned. I would say even that one probably doesn't full fill what you are describing, cause I'm looking for the same kind of mod. I hope one of the lynch modules will satisfy...
XTC module with cap mod to tighten up the bass
155$ shipped
Top Boost, no mods all original 145$ shipped
Plexi module, no mods all original 145$ shipped
looking for a 1086!