@matthew flego
Trying to answer in order ;)
I have no experience with Eagle since the autodesk switch. That said I'm very happy with the ecad/mcad capabily of kicad. Their partnership with freecad rocks. I'm using Inventor and autocad for mecanical things mainly because I learned CAD with them (you can have them for free with a maker licence). I tried fusion but coming from inventor I was a bit "meh it's a downgraded inventor". Inventor eats almost every cad formats (only sketchup is giving me troubles)
Use what you know is the way to go.
Cable wise, the VGA idea was to use the cheapest-high-pole-wire. But they're not 15 polespin-to-pin. I should have checked that... I'll have to do them myself. That's why I don't recommend going this way.
USB are cool but you'll need one for each motors, add endstops + actuator and you'll end at about 10-12 cables.
I like using ethernet cables too but again, not enough pins on this case.
D-Sub 37 could be an option : 6 motors*4 + gnd + vcc + 6estop signal = 32 pins and 5 spares
At the condition to find pre-made wire as they are a pain to solder/crimp.
Regarding the drivers, yes integrated drivers are a valid option.
I would use trinamics: https://www.trinamic.com/support/eval-kits/details/silentstepstick/
They're the most silent but not the cheapest.
These ones are very good for the price 30V 3A, supports 3.3V and 5V logic: http://www.panucatt.com/product_p/bsd2260.htm
I use a meanwell 24V 10A and a Traco 5V 5A powersupply. I salvaged them trough work for free so... ;)
but yeah a 24V to 5V step down could be a good idea.
That said, the 5V powersupply is IMO not needed if you don't use many 5V relays: the arduino can be powered by the computer.
I'm tempted to make a board interfacing a 32bits arduino (due or better adafruit grand central) with 6 drivers mentionned early.
But first I need to make my arm move ;)
