Thanks for the thoughtful reply. I am surprised about the performance because my other 10 year old pc manages much, much better. That one has a Core 2 Quad Q9650 (3.0 GHz) a GT 730 and also 8GB of DDR2 memory.
I'll end up keeping the case, ssd and psu (its actually the same PSU you recommended and now that I remember its the only thing I bought). So I'm on the hook for CPU/MB/RAM. I'm guessing from your build you think the Ryzen integrated graphics would be OK?