Yep, definitely the Max. Thanks for the link, will definitely try! If it doesn't work, I may just go for one of the two you mentioned, I've been looking at those two anyway.
I just built a PC with the following:
MSI B450 Tomahawk Max
Ryzen 7 3800x
NVIDIA GeForce RTX 2070 Super
G.Skill Ripjaws 4x 8GB DDR4
Corsair RM750
I've tried two different CPUs in this (Ryzen 7 3700x and 3800x), took everything apart and put it back together three times, tried starting with...