I’ve just done a cart list for the bi amp only change coupled 4345 final schematic.

Pcb parts only
On my list l selected a Jantzen laminate core 1.8mh. All other inductors air core
All Solen capacitors
Dayton audio grade resisters

The total parts cost was US$309.64 or a pair of networks excluding shipping.

Most forum members with these systems have already built or had built by Giskard charge coupled networks.

If you are new to all this l would look at installing the network internally to save a heap on money and space taken up by an external network. An external network won’t make it sound any better. Wiring faults are more likely with external connectors and cables. The pcb should fit on the inside of rear access panel. An external crossover will need a reasonable sized enclosure. Most people who have done this either put them atop the loudspeaker system or beside it. Will that fit the room decor or WAF is something to consider.

Given these particular pcbs add almost 100% to the overall cost and if located internally (not mens eye candy) a conventional plywood crossover assembly would be a significant cost saving.