I guess I'm just trying to work out for myself if what I've thought for quite a while is a good idea or not. Since I like a tight, controlled low-end, I've often chosen cabs that do that, and then occasionally paired them with heads that are anywhere on that spectrum. I never boosted low-end on the LMII because it was already so full to begin with. That lead me to want an IP310 since folks always claimed you would never need to boost lows with it. Boy were they right!

Instead I was looking for ways to remove lows without killing the tone. Finally just gave up, although I think a good HPF probably would have done it.
Back to the LMII, I think maybe a big reason why the RH450 seemed to have more absolute volume had a lot to do with the tighter bottom such that I could turn it up more. Maybe the stress I attributed to the LMII at the time was actually the cabinet not liking all that extra low-end content. With both the RS212 and Neox212,
the RH450 could be cranked, and it just drove the cabinets harder. The Shuttle 6.0 was as loud as the LMII, but it didn't have quite the same amount of punchy bottom. Engaging the LF Extension on the 6.0 took a bit of the usable power away from the 6.0, and it seemed to make the end result feel less punchy as a result. With the 9.0 however, the head never flinches even with that extension enabled, at least not at the wattage that the AE212 can handle. But as you ease the volume up higher you can definitely hear the cab unloading that low end in an increasingly unpleasant way. I haven't pushed it too hard because I'm a bit nervous about what could happen. What's so cool to me is to hit that little button and make it all go away. Volume stays the same, low-end tightens up, and I'm good for another 5-6 clicks on the master, even if I boost lows by 2 or 3db.
It's way cool.