Thank you, this has been super helpful. I've been looking for just this kind of info for about month now. After experiencing how disappointing the Layla sounds out of many TOTL daps and sources. (Balanced in general doesn't work for it - I suspect the loads become too much. Also, and surprisingly, Mojo alone can't handle it.)
If I could just pick your brain for one more thing - how would you compare these four sources soundstage wise? Width, depth, 3d effect with the Layla?
If you are not getting a good sound out of Mojo stand alone, you probably have a fit issue. It's a pretty good pairing imho and not dark at all. If you still have the Mojo, I would try different tips until you get the sound you like. If you can't get a better sound with different tips, then your ears may not be a good candidate to pair with Layla and maybe better to go with Angies.
As for various combos and impressions:
Using Mojo as source and Pure 2+ as amp, I find the presentation very intimate and in your face. The amount of detail and depth is amazing, but the sound is more like standing in the middle of the performance. Big on wow factor, but hard to listen to for extended periods for my preference.
CDM and Mojo is not a good combo and I agree with
@FidelityCastro on that. I don't believe it's a fault of Mojo, but rather the SE input on CDM. I find this combo worse in every way compared to Mojo/Pure 2+.
CDM as a stand alone with Layla is a great pairing. Soundstage width and depth are not the largest, but very well balanced and natural 3D like presentation. This is with Sonotone tubes and using balanced out.
Mojo alone is very similar to the combo with Pure 2+. The Pure 2+ extends the highs and lows more than Mojo by itself. I know this sounds counter intuitive but it's very noticeable. In fact, pairing the Pure 2+ with the AK240 SE output gives you a really nice experience with the Laylas. I don't know how the Pure 2+ creates the perception of more detailed highs, but it does.
The very best setup I've heard is my Gungnir Multibit DAC balanced out to the CDM balanced in. This combo with the Laylas is simply stunning. It's the CDM plus wider/deeper sound stage and incredible details. I haven't listened to my Ether C in a long time because the Laylas in this configuration is so good! Not practical for portability though. I am this close to just selling my Ethers and MJ2 amp.
My recommendation for the best portable setup in order of preference would be as follows:
1) Cheap transport (like Onkyo DP-X1) USB OTG connection to CDM, balanced out to Layla.
2) Portable DAP of your choice paired with Pure 2+ amp to SE Layla
3) Cheap transport (USB, Toslink, Coax) connection to Mojo to SE Layla