Hey Dave,
TrueRTA does waterfalls ? I bought it a few years ago (and a calibrated MIC) but I do not remember a waterfall feature. I have not used it since I set up my room. I will have to dig it out and take another look.

Microapp, Thanks for comments. I've done everything in your post but put anything on the ceiling. I have a drop ceiling with acoustical tiles. I thought that would be enough.
 
 As for the waterfall, I found the graph for that and will try to post it tomorrow. I'm heading to work.

You graph starts from ~500Hz, as I can see, it is not right, the most problem interval is 0-500Hz.
Also usually more smoothing is used for such graphs.
You can find some tutorials how to use it.

You are correct ADQ. The graph is so blurry I took the left few lines to be low-end octaves.
So we do not really know what the low end looks like.
I thought it was unusual for a small room with no traps.
 

This is a spectrum from the sine wave sweep. Much bigger picture." />

Barczar,
This still looks OK down to 50Hz with the exception of a dip @ 85Hz. The uneven sub-bass is probably standing waves and also your speaker roll-off. You might be able to improve the sub-bass with traps but to do anything substantial you would prob need helmholtz resonators or mass panel resonators and not sure you would hear much diff.
I know it seems counter-intuitive that absorbing bass could even out a dip in bass but in a small room the long lo freq waves produce nulls in certain areas. Absorbing these freqs reduces the standing waves and actually flattens the response at these freqs.
The 85 hz dip is prob due to the room dims...hard to tell. If any of your wall to wall dims are 12-13 ft, this is possibly the cause of the 85 hz dip. Could move your desk a little out from the wall if this is the case...may help a little.Try moving the mic and retest before you go overboard though. You may get another dip. Small rooms are a pain.
Overall this still looks good for a static test. I would say go make some music.

Thanks Microapp, I really appreciate your input. You seem very knowledgeable on this subject. Do you think I can use my ARC 2 to correct for the rest of the bass deficiencies?

Barczar,
I took at look at the ARC2. I think it is primarily for mids and highs. I say this because they claim it corrects not just for mixing position but the entire room. This is not really possible for low freqs unless you have some device or means to sense your listening position in the room.
THe fact that the ARC2 uses multiple position measurements in its correction algo is pretty slick. But still for lows, correction is not possible for the entire room at once.
I do not recommend the old analog graphic EQ's to fix a room especially for mixing. THe phase issues inherent in the bandpass filters is usually worse than the problems with the room. Digital filters like in the ARC2 can eliminate these filter phase issues.
I would say try it and let your ears be the judge. It could certainly help with highs and mids.
I am interested in how works for you. Maybe you could keep us posted after you give it a spin .
 
 

One more thought. Try the ARC2 with a few mixes and get them to where you are satisfied..  Make demos. Listen to the demos in as many places and on as many different playback devices as possible. Do your mixes sound good and consistent in all cases? 
This is prob the most important determinant of how good your room is.
 
 
 
 

I'll try the ARC 2 and report back. I guess it wouldn't hurt.
 
 Thanks for your time and advice.
 
  BC