No expert as you know but just a couple of things, will you get away with running 2 motors from one outlet on the power supply which you will need to do as there are only 3 on the power supply you have. Maybe Jazz or someone will answer that.
What are you going to use to connect the breakout board to the drivers? I have actually used 4 core cy cable myself but not the 1.5mm which is to heavy, bought a couple of metres of 0.5mm for that. Same place you have listed so easy enough to buy a metre or two.
3.1Nm motors will be ok for this, they have been mentioned in a few of the threads for 2 motors on X axis.
Cable from pc to breakout board is about the only thing you havent mentioned. Not sure if the fuse boxes actually contain any fuses though or if they are just used to protect the strip connector that joins the short motor wires to the cy cable. Looks neater than a bit of chocolate block as well so may be the only reason.

ps. I live in Scotland so at least I should be reasonably safe on Sunday when Leicester goes into complete meltdown lol.