Anyone who has to ask what PC to build and hasn't already got a 5k specialist system is unlikely to work in enough professional capacity to need 64gb, and it's easy to always add more if needed, just go for 2x16gb sticks. If they needed it they would have known by now.
I guess £150 motherboard isn't a lot but then again, that PC will run just as well on a £50-100 one, I use base 3900 (non x) so have to overclock it and I do it on a budget £100 x470, running 3900x stock settings will work just as well on B550 as it will do on A320 and literally anything in-between. I run 2x NVME's as well and don't seem to miss a 'b550' or 'x570' at all, saved myself £150 there alone. A decent b450 for £80 would be plenty. And yeh yeh PCI-E gen 4 bla bla argument, let's be honest, nobody will use that anytime soon apart from people running servers, VM's and other specialist projects that run into bandwidth bottleneck and even then, go for x570 or threadripper if it's really an issue.
Nothing wrong with what you've suggested at all, it's a great rig, but I am just saying the money can possibly be spent better elsewhere, or just saved.
A good monitor will be a much better investment imho if they don't already have one, for all we know he could have a cheapo 1080p
.
Obviously that's for the OP to decide but just something to think about as clearly they have a budget to stick to and there are few options to go around it.
