Hi,
I am a member over at the above mentioned forum....
Here's what I can tell you...
The STR DA3100ES is a analog amp receiver...the only class D receiver they now produce is the 7100.....the 9100 is rumored to be close to production.
The 3100 is pretty much (by most accounts) a copy of the DA4ES....but lacks the flexibility in bass management, and EQ that the previous DA4, 5, and 7ES offered.
The 2000, 3000, 5000ES models have been discontinued and were digital class amplifiers...
Recently it seems that most of the 3000ES units that have been shipped from certain vendors have been faulty, However the members that own 3000's that are not faulty really rave about the digital sound...These units also lack the flexibility of the 4,5,& 7ES.....
Hope this helps....