Finally, I have all 96 holes drilled in the steel plate. I also started to tap the M5 threads.
As I am lazy I have used my cordless drill and when I got too excited I broke the tap bit.
I ordered new ones from amazon and while I need to wait for them I thought I take a look into the control box.

So this is my control box and it looks nice from the outside.

Also, the back side is nice and all the connectors properly marked.

When I looked inside I was surprised in a positive way. I have seen some other Chinese CNC control boxes on youtube and in CNC forums. They looked like someone did just throw in all parts.

This one looks really good. All the components are mounted nicely and properly. The cabling is done well. That looks clean and professional. 

Tha Mach3 USB Board is the BSMCE04U-PP from Bitsensor.com. I tried to look up their website, but you get redirected to a Chinese shopping portal. The board name did not bring any really useful hits on google either.

But this board is sold on eBay as "MACH3 4 Axis 100Khz CNC USB Breakout Board" for around 20€ including free shipping.

There are 4 single motor drivers with the Toshiba TB6560 chip, each has its own heatsink. You can find similar boards on eBay between 5-20€ rated up to 3A.

And then there is the VFD that controls the spindle motor, which is just the board and not a complete VFD wich chassis. The ribbon cable connects to the control unit in the front of the control box.

At least this is rated to 1.5KW according to the stickers.

And here is the backside of the VFD control unit.

And last the power supply. I did not check if there are any marks to what power it is rated.

Maybe I do that to a later time. But there is a raiser shield to have the VFD board mounted on top of the power supply and a think aluminum block for the VFD board.

For sure not highly sophisticated components, but the work.

One thing I had on my mind for two days now is to replace the Nema 23 stepper motors on the machine. It still gives me sleepless nights that the z-axis lost steps when I tried to drill the holes in the steel plate.
The easiest way would be to upgrade to close loop steppers. I found the JMC iHSS57-36-20 closed-loop stepper for around 90€ and the driver is mounted directly to the top of the motor.

Compared to a driver/motor bundle from Leadshine which costs around 150€.

In theory, I would just need to replace the original Nema 23 with them and it should work fine.
But for 130€ you can also get the JMC iHSV57-30-18-36 180W integrated servo motor.

And I guess I might try the servos rather than the closed loop steppers. Even when it seems that there more difficult to tune to the system.
Either way, with a closed loop system, stepper or servo, there should be no more lost steps and those models have much more torque than the original Nema23 steppers.