I've navigated the next leg of the journey.
The Aguilar DB-925 is gone. I liked the sound it gave me, but it was kind of a one trick pony for me. The inability to cut was the main reason for my decision to get rid of it - I liked the sound I got when I slightly boosted bass and kept the treble at zero - but nothing else. I did not get it to do anything useful in combo with a fully grown preamp.
The EBS Microbass II is gone. In direct comparison with the Microbass III, it just felt that for my usecase the III is superior to the II and there's nothing to gain from keeping the II.
The Mesa Boogie Subway DI is gone. As I wrote earlier, we simply did not click. It does what it is supposed to and I can coax usable sounds out of it, really nothing to complain about, but no fat grin on my face either.
So the winner of bout one is the EBS MicroBass III. In fact, I could stop right here. This unit feels like a nice addition to my collection and I'm happy playing with it. However, I feel like I want to try out some more before settling down. It is nice to know that I could stop, though.
With the EBS sitting in the champion's corner, I eagerly await its competition to arrive later next week.
The challengers are:
1. The One Control Crimson Red Bass Preamp.
I really like the sounds I hear from the demos and would try out what it has to offer - the risk might be that I reach the same conclusion I did with the Aguilar - but the One Control can be ordered with 30 days money back, so there's no risk.
2. The Tech21 Q\Strip. I liked this pedal from the day it was released. In theory. I've never heard it.
3. The Trickfish Minnow. At first glance, It is quite similar to the Q\Strip. Shelving Bass and treble controls, two mid controls (parametric on the Tech21, semi on the Trickfish), but it runs a lot hotter on the power supply which might or might not mean that there's more headroom to be expected. I've found a deal on one that's good enough to snag it up and sell it on, should I not be satisfied.
I will keep my eyes open for other options and see what pops up, but I want to try the Q\Strip so much, I'll order it new if the auction does not end in my favor.