The information at Digitec is not always 100% correct, because mine has an RM750x 750 watt power supply unit in it.
Since the system draws about 580 watts at full load, a 650 watt at 80% efficiency would already be overloaded.
The 750 watt should be just about enough, however, if you install too many additional holes or overclock excessively.
In any case, it runs stable with 2 additional NVMe SSDs and overclock (CPU 5.2Ghz and GPU at 120%).