I finally got around to read the book titled " Designing, Building, and Testing Your Own Speakers System" by David B. Weems... Overall a good book since it helped me further fine tune my 2 Pi towers and I would like to share it with the group. Here is what I did:

From day one, I always thought my 2 Pi towers was a "little" bright and loud... this could be due to many things, speaker efficiency (a good thing), room acoustics (not much I can do), etc
Anyways, one of the things that David Weems noted in his book was that if the speaker sounds loud chances are it needs more insulation. Since I already have three of my internal walls ligned with R-13 insulation I proceeded with filling all four sides with insulation and sure enough the sound got much "quieter" to a point that it lost all the sound stage I came to associate with the 2Pi tower. After further experimentation I ended up with insulation on three sides and the fourth side is insulated except for the top 1/5 th of the length. After this experiment, I noticed that not only I was able to maintain overall staging, the 2 Pi is not as loud as before, but also there is now added depth to the sound which is a big plus.

I now find my 2 Pi's even more enjoyable!!!

P.S. Some clarification about the insulation on the fourth wall. The fourth wall insulation in my case is the side wall starts 9 inches below the the top. Also, I've tried to increase vent depth by 10 inches and did not notice any increase in bass. Happy listening.