So I started the surgery early yesterday, and after about three hours I was finished up!
The No Rez cuts I made with both my utility knife, and my bare hands, are not the prettiest looking pieces at the ball, but no one will ever see them.
Interestingly enough, AV123 had actually put some No Rez in my cabinets. I would say 2/3rds of the side walls were covered as they should be. Nothing as on the bottom or the top.
I only ended up needing three sheets of the No Rez total. So I have six sheets left over.

I also added poly-fill from walmart to the entire cabinet. I ended up using about 8 pounds of it or so total.
The sound is completely changed. I am actually shocked at the difference.
It sounds like a completely new set of speakers. I don't know if my sense of accomplishment added anything to what I am hearing, or if these speakers are just this fregging good.
The bass sheer output level dropped, but the tautness went up a few notches.
This change in the bass output, and I am assuming the new control over resonances, just opened up the midrange beautifully. Transparent, open, with some pretty excellent vocals....
Overall I am pretty pumped about the difference. I just want to go home and listen to music!!
I hope things stay this awesome, and when I get home the difference was not at all induced by hubris over my first (quite insignificant) DIY "triumph."