Haloxt,
There is quite a few differences between the DAC19SE and DAC19MK3, in DAC19MK3 you have the additional USB connectivity apart from optical and coaxial, it uses a redesigned board and most importantly the newly designed CAST module which makes a difference sonically - all this in a convenient desktop size all aluminum chassis.
Whereas the DAC19Se is a more conventional full size DAC which has been in production for the last 2-3 years and upgraded in early 2009, it uses the old CAST modules, it does not have the additional connectivity like the DAC19MK3 as it only has a single Coax RCA and BNC input. But there are a couple of things that the DAC19MK3 has, like a more powerful transformer and separate power regulators for each channel and this is the reason why it sounds at least as good as DAC19MK3 according to Kingwa.
Putting aside the differences in SQ between DAC19SE and REF1, if you just take a look at the interiors of both, you will quickly realize that much has gone into the REF1. Its not just about the 2 X PCM1704 or 8 X PCM1704, but much more in form of pure power (3 trafos) separate boards, advanced circuitry and processing of signals, weighing 3 times more and costing as much from the same manufacturer, who says if Compass DAC is 1, then DAC19SE is 3 and REF1 is 10, and you cant compare the DAC19SE with REF1, obviously he isnt trying to discredit his own design but I think it explains the reality - which is what I found myself while comparing the DAC19SE with the REF1.
So you are right, that there is not much if any difference between the DAC19SE and DAC19MK3 sonically - which makes me feel the difference between the REF1 and DAC19MK3 would also be similar to REF1 and DAC19SE.