I know this is heresy, but...

Undertow and Warnerwh,

How much acoustic panel treatments did you need to add before you noticed an improvement in the bass? Square footage or linear feet of bass trap? What do you recommend if you desperately want to minimize the amount of ugly panels covering walls. What is most effective in a corner...a Mondo trap from Realtraps?

Shadorne,
actually I have a similar trap to the realtraps, its from Gik, and it works pretty well when you span the corner as a hemholtz type should.. Cleaner response, way better Vocals in my experience, its weird but it cleaned up the lower midrange a lot too..
Beyond that I found that the panels minimum will be very dependent on the room size, actually a smaller room does take more due to so much reflection vs. a bigger space that kinda helps itself much more, not to say this is exact and that a big room can't benifit from many treatments as well.
Anyway I say Definatley killing the first point reflections on all sides of a speaker, via floor, ceiling, and both sides really helps. And some bass trapping in corners can resolve and increase response quite a bit too. Getting rid of any echo is key I noticed as well, but all this is relative to listening position, how much furniture, and what kinda space you have I would guess.. I am not an expert at all, just now realize the common sense benifits of even some simple treatments.. Diffusion etc.. is a whole other thing, and basically keeping things pretty well balanced seems to be the key.. Also, I kinda notice if a room looks like it will not sound that great or feels it, then it will not sound that great. Some care in setup can go a long way I guess, but I have limited experience in only about 4 different areas that I have somehow got to sound pretty dam consistent vs. when first just sounding like crap.

Shadorne, by the way I just saw your setup, and being everything is like flush mounted, and other issues being inside the walls etc.. with a pretty good sized area, and very Hard walls built around everything, you would be almost forced to maybe try something with return policy or get the professionals at Rives audio draw you up something very effective.. I could say this you have a very non traditional type install for the guys running 2 speakers out in the middle of the floor looking for 3 dimensional sound, I know enclosing my speaker cabinets into another cabinet within a wall would restrict a ton of air and space.. So you may be best just going after the most Bass trapping possible with aesthetic appeal you can in that room and hope for results with your subs. Or add a lot of large couches! But seriously you have a very different and other set of issues the traditional crowd probably does not deal with.

So you may be best just going after the most Bass trapping possible with aesthetic appeal you can in that room and hope for results with your subs

My thoughts exactly. Big rooms are generally better than smaller rooms but they can suffer from very long reverb times in the bass (end to end). Currently a PEQ has all the room modes well under control but my thinking is that it might be better (more natural sounding) to do more with bass traps on the rear wall to dampen long reverb (about 10 feet behind the listening position). I am struggling whether it will really do much to improve the extreme LF?

FYI: I am generally very skeptical of tweaks but following advice on a Genelec website lead me to be pleasantly surprised. The other thing that convinced me was Doug Sax Studio. Doug won a life long achievement award from AES for his work on audiophile recordings (Sheffield labs etc.) and he built this studio in 2004 with soffit mounted speakers in a half wall.

Shadorne...Rives audio, who certainly are great believers in room treatments, will tell you that low frequency problems can't be fixed this way. That's why they developed their PARC equalizer. The only really "correct" way to deal with LF room modes is to build a special room with ideal dimensions and no square corners. But few have the time and money to do this.