Got your pro version right there. 
/edit: Whoops, late to the party… 
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I saw this video the other day. There seems to be some choices between closed loop nema17s that Teaching Tech used and the servos that This Old Tony uses:
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Oh those look too easy!
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These closed loop steppers (with optical encoder) on omc-stepperonline.com advertise having 113.29oz/in (80Ncm) and they are listed for $22.36 each when buying a set of 5 or more, and delivering from stock in the USA. (Cheaper when delivering from overseas, apparently.)
By contrast, the open loop steppers that @vicious1 sells in the store for LowRider are listed as 84oz/in, but priced at only $11.50.
If those closed loop ones need pricey drivers that should also be considered.
Overall price difference sounds “not bad” for a “pro” version machine.
??
What would be the next point of failure when there’s that much torque in the steppers? The belt mounting blocks ?
Possibly. Also, I can see bits breaking.
I used to have the beefier nema 17 (92ozin) -open loop in my old lowrider 2, these motors will rip the belts or the belt blocks first thats for sure.
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Good question. In my case, this is on the Z assembly only, with a leadscrew. So ripping up belts or belt blocks is not an issue there. The lead nut may come unmoored, or the coupler may slip. I did ram the collet (no bit installed) down into a piece of wood once since I installed it, by accident. It made quite a dent and I saw deflection of the Z assembly (slight bending of the pipes and the Z core plastic??) before the driver threw a “position error” alarm and shut off the stepper. I suspect one can go into the firmware of the driver and set an over-current protection that would prevent serious damage to the machine.
I have tested out the new closed-loop Z stepper & controller carving terrain and it works fantastically. Here is a video of it carving at 75mm/sec in X, Y and Z, and I even increased it to 100mm/sec near the end of this finishing pass with no problem. The whole finishing pass took under 2 hours, where it would have taken over 6 before.
The stepper motor does not get hot, I would guess less than 30C.
The whole MPCNC current draw (all three axes) is about 1.5A (40V) while it is doing these carvings, even during the roughing pass that is pushing it pretty hard.
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Wow, impressive!
Thanks, and welcome, Briana! Well summarized.
Downsides are the bigger price and size of both stepper and controller, compared to the stock V1 kit.
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Steve, do you know whether I can just swap the steppers if I bought this kit:
Or do I need any other hardware?
That is very similar to what I got for my Z axis. The only extra thing you may need is a more powerful or higher-voltage power supply. This driver can go up to 48 volts and you should do that. Higher voltage means more torque for less current (so less stepper motor heating). The closed-loop stepper driver does not seem to get hot at all, so passive cooling via its heatsink is fine.
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Thanks a lot. I’d stick to 24V first and see how that goes. Since I have been running the Primo on the Jackpot, I want the other one to be more quiet as well. 
Proceed carefully with this switch. They put it at 24V by default because if you have a microcontroller that emits pulses and control signals (dir and ena) that are greater than 5V, this would blow the controller if it is set to 5V. I would measure the actual voltage of your control signals with an oscilloscope and set it accordingly. I am using a Teensy microcontroller that emits 3.3V signals which seem to work with the 5V setting.
Okay. I think the TB6600 are using 5V as well. If I set it to 24V but my controller is only sending 5V they just won’t move, right?
So I could start with that and flip the switch if it doesn’t move?
Okay, I have yet again another question: if I bought the kit above I’d pay a lot of shipping and taxes. I can buy nearly the same kit (a bit better) directly from stepperonline on Amazon but there are no extension cords. Can I just cut the connectors and crimp the cables normally, or would I destroy something doing that?
Cheers again!
Also, I don’t understand the price difference, the one being the “P-Series”…
Those look like just the stepper motor. You need a matched CL controller. Amazon: BEWARE of fakes. It is worth getting from Stepperonline directly. I make all my own cables, using shielded cabling. Old VGA monitor cables are good for the encoder. You need 1mm copper for the stepper motor phases, though. If you are good at soldering and crimping, make your own.
I know, but the Nema 17 set (stepper driver and stepper motor) is not sold by Stepperonline in Germany, it only ships from China and with customs it would be really, really expensive. So I opted to buy the stepper and driver as single purchases. The drawback: it does not have the extension cords, hence the question whether I can just snip the plugs and use “normal” cables.
I am not good at soldering, I’d just crimp the wires after cutting them. The VGA-cable tip is great, though, I still have lots of them.
Thanks a lot!