Very interesting. I always felt the MK1 had better quality bass than the MK2.

It does.  We just have bigger ear canals than Marv for the requisite insertion depth.  It does have roll off but the mk2 might be less rolled due to the midbass elevation?  The bass quality is inferior for sure on the mk2.  Not too dissimilar to how my ears respond to the HE500 tbh.

Interesting observations From my point of view, choosing the right tips is much more important than bass difference between 1 and 2. The housing is different, and so, same eartips will make different  effect with mk1 and mk2.
Also, from technical standpoint, if anyone is curious, mk1 and 2 is absolutely the same. Only difference is slightly altered nozzle and cable.

Does the nozzle use a different filter?

No. You know, I was working on finishing the mk2 production, and I did not want to touch the thing that is working good already. And so the filter is definitely the same as on last DBA-02 mk1 bunch. I am not sure about the first bunch of dba, as I was not working on FA when it was released, but last bunch was the same, and I compared them. Yea, mk2 have slightly less brightness, and bass is acting somewhat differently. It is because the nozzle have different geometry (length and angle). Also, I would not be surprised, if soft-touch alters some plastic parameters, like density and resonance point.

Btw, any thoughts about making a higher end DBA/B2?  More bass extension would be nice.  I'd favor another two driver or four driver.  Three drivers tend to sound noticeably incoherent to me, every single one.

TBA-04 is soon to be released... At last. It is not an improved DBA-02 however, and is totally different. Mid-centric I'd say. It will be a short run, we have some much more promising designs.
Improved DBA is one of them. But, problem is, we do not want to give this designs to china factories for several reasons.. So it all comes if we able to settle a local production. Which is terribly painful in Russia...

Ever thought of making a dynamic using the GR07 housing?  Love that design. 

Yea, I find it pretty cool too. But no, it is doubtful we will make something like it in near future. Such housing is simply to expensive and difficult to control for us, also such design have questionable effect on sound quality. And benefits are.. not that vital.