That CDX 1745 is a nice little driver. Looks like it could be considered a drop-in replacement. Honestly, I find that most compression drivers can be used and many have the same voltage sensitivity. For those that don't, a simple R1/R2 switch usually gets the SPL right.

And speaking of that, you're right that the Delta Pro driver has higher voltage sensitivity. We specify the R1/R2 values for that driver to lower the output of the compression driver accordingly. But I didn't change the three π schematic to include those values until sometime after finalizing the updates described in this thread. So any plans that don't show the R1/R2 values required for the Delta Pro driver have an older version of the schematic.

I don't think I'll evaluate B&C midwoofer options for the four π model. I do like their products, but I really like the JBL 2226H too. So what has sort of developed is the three π and six π are for people that prefer B&C, and the four π and seven π are for people that prefer JBL. Both are excellent choices, and it's sort of like a Ford vs. Ferrari thing.