Hi Musicmann: I can somewhat explain the difference in the Chang 3200 product only. The original MKI has what they call a "quad filter" for each of the 4 analog outlets; the 2 digital outlets are not filtered, but they are still protected by the internal MOV line-transient snubber. In the MKII the digital outlets are now filtered also, but to which degree I don't know (Chang has various filtering levels - double filtered, triple filtered, quad filtered, etc).
Also the MKII filters are claimed to be better than MKI's. Their website info explains it like this:
The new MK II powerline filters surpass former models by providing:
More precise imaging
Increased inner detail
A more three dimensional sound stage
Lower noise floor for a darker background
Greater dynamic contrast & "Slam"
Increased picture depth perception
Increased video Detail
Increased color saturation
Improved color rendition
Increased surge clamping capacity
One thing that I prefer about the 3200/MKI is that since the 2 "digital" outlets are not filtered, you can use filtered AC cords there without having "excessive filtering" issues (the Chang filters + the cord's filters can sometimes be excessive when used together & actually degrade your sound). I use them not just for digital, but for any source component that sounds better with a filtered cord (such as a Custom Power Top Gun AC). Specifically in the CD player situation, I use a filtered JPS Digital AC cord plugged into the unfiltered digital outlet. If I use a filtered analog outlet + the JPS filtered cord then the results sound constrained.
Regarding the rest of their product line, as mentioned, I don't know the full differences between MKI's & MKII's so call Chang for further details & please post their responses here for everyone to read.