Noctua NH-D15 has quite a bit better cooling performance than be quiet! Dark Rock Pro 3.
What exactly do you need from an MSI Z370 Gaming Pro Carbon that you couldn't get from an MSI Z370 Gaming Plus? The only real difference lies in the CPU channels.
The Gaming Pro Carbon will generate a little less heat, have a little higher lifetime and supply a more stable voltage. If you're an extreme overclocker and want the absolute best clocks (which also have diminishing returns) then sure, go for the most CPU channels you can get. But if you're fine with not getting the absolute best (in which case you should also delid your CPU, get more CPU fans and a high end AiO cooling solution) then I would say it's not worth paying 80 Euro more.
Also, get rid of the 750W power supply, get a gold rated 550W one. SeaSonic G-Series G550, Corsair RMx 550, EVGA SuperNOVA G2 550.