Thanks Jeff - let me wrap my ahead around this info and post back. It's about bed time... :)

The stereo tracks would also work.  I am not saying it can only be done with the mono tracks.  What I was really trying to get across was the concept of doing two identical mixes on two different environments. 
 
You could in fact send out 8 stereo pairs for example to the analog mixer that is OK for sure. But all the faders maybe should be at unity in the analog mixer and you adjust the mix by adjusting the clip gains of the audio files perhaps on the stereo tracks themselves.  (Can you send out the track outputs to your Midas after the faders in Sonar) That might be another way.
 
When people are sending out tracks to a summing buss they are doing the mix there.  Either by adjusting the summing buss levels or leaving them all the same and adjusting levels within the DAW from the tracks. That is all good.  But there is nothing being compared to though.  So to say that a mix sounds better just because you are sending tracks to a summing buss is not necessarily correct.  Because you are not doing exactly the same thing ITB  the box and comparing it. 
 
But we are trying to do a test here that is comparing the two things so there must be exactness in terms of the mix levels in both systems for the test to be really valid. This is not happening so far in your test.  I see that there is not a perfect match between those two things mix wise so in a way it is too hard to tell.  The waveforms are just too different.  I noticed that straight away.
 
We need another approach to accurately create the mix on both systems.  The closer they get I am wondering how different they will actually be.
 
Back to my link.  Post 2. All the guys in the room picked the best mix as the one that was done ITB. That says it all don't you think. It does not matter if its ITB or outside the box either.  It still all comes down to how well someone mixes in the end. 
 
And even if consoles are doing things like adding crosstalk etc what about the fact we are into an era now where they are emulating that already. 
 
I used to mix OTB. I had 24 outputs feeding a large Tascam mixer.  I have drifted the other way now and gone ITB. (As also many top name engineers have as well) I feel I am doing my best mixes ever right now. It is not due to them being done ITB either.  It is because I have become a better mixer.
 
You may be wondering why they still do things on large format consoles. It is for other reasons. The Neve summing box has transformers in it. That is what you are hearing. A Neve console has got a transformer on every input channel. That is what you are hearing. The EQ's and things in these large consoles are often well designed and sound excellent. I am not convinced it is the summing part of the mixer that makes them so great. They are now emulating all that with Harrison M32C with that lovely EQ (and UAD) and the SSL channel strips you can get now.
 
In fact I was reading great article in SOS a few months ago in the Studio One column on the CTC-1 console shaper. They tested a whole lot of large format mixers, just the summing parts only. Neve, SSL, API etc. They said there was no noticeable difference between any of them and in fact they all sounded amazingly neutral. That is interesting. That pushed them to look elsewhere in the mixer sound.
 
Too much emphasis in my opinion placed on just the summing buss of any analog device. The sound of the mixer is everywhere else. e.g. the lovely EQ in your Midas etc.. Which we are not using in your test. That is why if you can get two perfectly matched mixes I bet it will be very hard to tell them apart.
 
Don't let me deter you though. Keep on it. It is fun and interesting. I appreciate the effort you are putting in.

OK, so I took the time to get VERY precise with leveling all of the channels. I also addressed two issues. The first was to set the bass up in analog summing just like it was ITB. The second was there was a synth that wasn't directed to a mixing channel in the analog summing experiment.
 
You will have to time-align these files to compare - the latency of going outside the box and then back in affects the timing of the file.
 
In the box: https://www.dropbox.com/s/ie57qcr1nwufyfk/ITB%2002.wav?dl=0
Analog summing: https://www.dropbox.com/s/hdrg2ycrjjjownd/Analog.wav?dl=0
 
Conclusion: the differences are so minor that I wonder which files I'm listening to! This method is not worth the effort.
 
Listen for yourself and let me know what you think! :)
 
Next I'm going to try going to Line In and passing through the Midas Pres to see if that adds anything special...

Besides the monitoring functions, the summing functions in something like the Dangerous D box could then be considered sales hype?

I have a Stam Audio 1073MPA on order and was considering running through that from the analog summing. But, after coming so close in the test there is really no reason to sum outside of the box. Whether or not running through the Neve 1073 (or a the SSL 4000 I have on order) adds to the process or not - so far there is no need to sum outside the box.
 
I'm going to try summing through the Midas pres tonight and hope to get files up shortly.

10/10 James for matching these mixes. You are doing a fabulous job at this now. Interesting thing is this is first time I managed to get some sort of null thing happening here with this one. Nowhere a full null by any means but I can get the low end to drop out now when I null these which means the bottom end of the mixes are matching for some reason a little more accurately.
 
As for sound still very very similar, very hard for me to tell them apart. Still no big OMG moment here! I am still finding the ITB mix to be pretty amazing.
 
One thing I am doing now that I did not do before is I am limiting how much low end I am letting into the room with my monitors.  Before they went down to about 35Hz but I am now only allowing them to go down to about 41 Hz or so.  After reading some articles about the benefit of not letting too much low end into a smaller control which is what I have.  I am liking my bottom end more as a result.
 
I have also got a pair of Yamaha HS7's (which don't go down real low anyway) Mixes sound extremely similar on those to me as well.
 
So if the bass end on one of these (maybe the pres) is little heavier I am not hearing it.  Maybe James you can clarify here if that is happening. 
 
Just done some more listening and maybe the top end a hair louder the pres but it is real close though. Nothing that some +1dB shelving at around 8K on the ITB mix would not easily match though. 
 

James,
 
Thanks for taking the resources and time to do this experiment.
 
I think many of us (especially "long timers" - read old ) suspected the results you're finding.
But... all these years later... it's still good to see/hear those suspicions confirmed.
 
There's no doubt that prime pieces of analog gear have that "something special".
I picked up a Neve channel-strip a while back.  Everything sounds better recorded thru it.
DI electric bass, vocals, you name it...
 

Thanks James it has been a pleasure and fun.  I have started to really get to know that track too!  There is nothing wrong with external mixing once you start using the EQ's for example on the mixer.  When I was mixing externally on a Tascam console I really liked the EQ's on the channels.  They were fast and enabled me to get the sound about 80% right very quickly.  Coupled with an EQ plugin leaving the DAW I was able to get sounds very easily.  Using the faders on the mixer is rather nice too. Nice to be able to just grab them and move them etc.. Having physical sends to reverbs and things is also rather nice.  But these things are other factors rather than summing engines alone.
 
Not sure pushing pres by 3dB will make things a lot different. I would have thought higher values e.g. 6 dB or more.  Pres tend to add less of sound when their gains are lower though so it might even make things closer!  
 
There is plenty of headroom mixing digitally especially if you work with something like the K system at a ref level of -20 dB FS = 0 dB VU. There is 20 dB of headroom in that situation which is only really available in the finest of analog consoles.
 
The biggest thing for me is the recall ability of digital though.  That in itself is amazing.  When I was producing a rather large project back in 2007 on a large format analog mixer I did have to recreate mixes like 2 to 3 weeks later because the client decided to change something.  Even after writing down every detail about the settings of everything on the mixer and the outboard I never got the mix exactly the same.  Analog works fine but it is best to put it to bed there and then if you can.
 

I was reading about summing mixers on the web, curious about them I guess and whether I could use a small Yamaha mixer as an experiment.  'Let me check the Cakewalk Forums,' thought I.
 
Thank you so much for this!