I just re-flashed my FW between 3.93b2, 4.07b1, 4.07b3, and 4.07b4.
I listed to a specific song on each FW and took note of the differences- which by the way were obvious. Then I repeated this entire process a second time and third time and took note.
Everything was done using my Mutec external clock, parallel mode, usb in from my iso regen and i2s out.
First of all- I am now convinced I was wrong about the 3. FW versions along with the 4.07b1 having more detail. 4.07b1 does seem to have the most detail retrieval at first listen and does have a very nice soundstage and excellent separation. However I now believe that 4.07b3 and 4.07b4 have either equal detail or very slightly less with a much nicer smoother more analogue tone IMHO; a kind of a honey glazing. I think the more sterile and harsh tone of 3.93b2 and 4.07b1 give the initial impression that the resolution is superior, but after going through this process and comparing the FW's multiple times, I don't think I'm loosing much in the resolution department with 4.07b3 and 4.07b4 if any and it just sounds noticeably more pleasant to my ears.
4.07b4 is more focused and has fuller, more powerful sound while 4.07b3 has the same basic tonality (honey glazed) as 4.07b4 but with a wider soundstage- further back in room feel.
I could really see how these perspectives could change with different system factors. Just to give an example of one such factor, I use i-tunes in my mac mini to play my music. i-tunes provides a very non-colored colder style presentation and because of this I believe I appreciate the honey glaze of 4.07b3 and 4.07b4. However if I switch to Audrivana which has that honey glaze built in, I can easily appreciate 4.07b1 more because no more honey is needed.
There is no right and wrong here. Thanks to everyone for the fun conversation.....