Done upgrades so far:

• PSU (power supply unit) replacement: switched from the power brick that it was delivered with to a PC ATX PSU (Corsair CX500). The Corsair power supply has only one 12V rail which is important for using it to upgrade a 3D printer. Most modern power supplies have two 12V rails which means that their 12V output is split (unevenly mostly) between two 'power lines'. This is not good for 3d printing since the heated bed for example pulls a lot of power. With modern PSUs (unless they are in the 600-900W+ range), one 12V rail might not be enough to power the heated bed.
• updated the stepper motor drivers: to Trinamics TMC2100. They put out almost pure sine waves so the steppers run almost inaudibly! But: They also run hotter than standard stepper drivers so some active cooling is a good idea (see planned upgrades, i. e. cooling tunnel on mainboard).
• installed a power MOSFET to move the heated bed supply from the mainboard to the outside of the printer. This should decrease possible fire hazards through molten onboard connectors to a minimum and increase the longevity of the mainboard in general
• coated the extruder heat block in a few layers of thermo-isolating kapton tape - now the heating curve is a bit smoother and the extruder keeps its temperature more steadily

• designed and printed
• a preliminary fan funnel to cool the stepper drivers and plopped in a 50x50mm fan (a bit smaller than 2"x2") powered by the new PSU
• braces (Filament brace) to plug into the sides of a filament roll which take 608Z standard skateboard bearings. Now the filament unrolls much more easily (almost too easily ^^)
• and installed a filament filter
• a small retainer to prevent the bowden tube from moving backwards while the extruder retracts
• holding brace for the heated bed that mounts to the 20x20 extrusions of the printer

• downloaded and printed
  • a new and a bit fancier dial wheel (dial knob) for the control unit
  • elevated feet (elevated base stand) for the printer base that lift it up by 5cm (again, about 2").
  • cable holder (cable holder - my make of it) for extruder power line and thermistor wire. It snapped a while ago, need to print (and / or redesign) a new one

The printer still has a few calibration issues, mainly due to the heated bed. The heated bed has a few LEDs to indicate it is working but unfortunately, these LEDs protrude a bit so the glass plate on top of it is at a very slight angle. For small prints, this does not matter much but for larger prints, it makes a decent first layer almost impossible. See ToDos for planned improvement.