Can't think of any suggestions 'cuz you seem well on track right now.
I'd just re-add that you might make the base plate smaller. You'd have to TRY to tip them over even on plush carpet without any base at all.
If probs or potential probs creep up, feel free to post and people will try to help I'm sure.
Getting the face precut will make things real easy I think. Certainly that section of the speaker is where the most time is taken and the most flaws could pop up so cool to see that option for others.
Right angles, clamps, glue, some solder and be real careful playing 'connect the dots' when you wire things and you'll be set.
Good luck.
Couldn't say about the bass control with those amps, but Danny uses tube amps himself, and the Alphas take little power to hammer (if you want 'em too). (those Cary amps are tubes right?).
One Watt on these is already Loud so the power should be there for you on most amps. Really frees you to tailor the sound you want with your front end letting whatever you have shine right through.