In the meantime, regarding point 4: it did not occur to me that I could solder the big coil directly to the speaker terminal, especially to the mid-bass driver. Is there any specific reason for not putting it in the external XO box, but nearby the voice coil of the driver?
In answer to your question, I've got some Jantzen Superior Z-Cap and Kiwame 5W resistors at home to start with (plus Jantzen and Mundorf MOX resistors). Later on, I'd like to try Powertron metal foil resistors as well.
Since originally, this is a thread about hook-up wires, I'll report back especially on the cables as well. I didn't want to steer away from the topic, but this was the pllace where I could find the most helpful answers to many of my questions. Should I start a new thread?