Thanks so much for comments and advice received so far. Reflecting a little more on this I think building myself would probably be worthwhile - and more fun - and an opportunity to get up to date on latest kit / technologies. I want some fast / future proof and scalable (as much as one can predict what form that will come in) and have come up with the following below.
Questions for the hive:
1) Any "just wrong" with any of what I've put together?
2) On Motherboard I really welcome input - I likely won't be overclocking but really want something with as many M.2 ports as possible and is scalable in terms of numbers of drives.
3) On memory I was aiming 32GB of DDR5 but welcome advice - I'm really out of date
4) I have a Corsair Modular RM750x PSU I think I can reuse in this new rig but if not pls let me know.
5) I also have an R9 390 series graphics card I was going to use for now until I need something better - again let me know if that's a no go ...
6) On CPU cooling I only have experience using these Monoblock kits which worked well (until they didn't) but if there is something better that I can't mess up easily I'm all ears
7) On case I picked something with no flashing lights to scare the dog ... just after something that looks sensible and will fit but again welcome ideas.
1 - Your case doesn't have any windows so it's kind of pointless going for the Asus ROG Ryujin II 360 AIO, you could save some money and go for a non rgb and non oled option (you ideally need a window to see them) such as an ek basic for example (I'm actually running this plus 3xnoctua nf12x25pwm on my 5950x, the original fans are loud) at less than half the price. If you do want the rgb etc you need to change you case option... do you actually need something as big as the Phanteks if you're not running lots of hard drives?
I'd also maybe have a second small nvme drive for a scratch drive.
You'll also need case fans - I'd recommend, noctua, bequiet or phanteks 'quiet' fans.
Just something to consider (not sure on your budgets etc) - you're going to be paying a premium for that 13900k because it's the top of the line product, it might be worth considering dropping down one tier to the 13700k which is like £180 cheaper and you only really lose 8 efficiency cores... last I checked most adobe stuff still doesn't really enjoy multithreading over 8 (performance) cores which both would cover easily.
2 - I can't comment on current intel boards, I went AMD on my last build, but I agree with Tetras comment in respect to it.
3 - As someone who does 3D rendering which often includes merging with photo's etc I'd maybe try for 64GB ram, in a 2x32GB option, again you could save money with non rgb options as you wouldn't see them in the case you've picked...
4 - While it will likely be enough 'now' it wouldn't really allow any space for an upgrade on the gpu front imo. I also wouldn't be using it if it's 'old' either.
5 - Should be fine to get you up and running although personally I'd pick an nvidia card due to cuda (gpu accelerated stuff) being generally better supported than opencl that AMD cards rely on.
6 - With the amount of heat that the high tier cpu's kick out these days, you're kind of being restricted to aio's and a small selection of large sized air cooler for what you can use for cpu cooling....purely because a lot of air coolers just aren't 'good enough' to handle the heat they can produce.
7 - you picked a case with no flashing lights (good choice, I don't really like that vibe either) but you then went a picked a load of stuff that has rgb on it which you wouldn't see AND you pay a premium for over non-rgb stuff.
Unless you intend to add in a load of 3.5inch drives you could likely go smaller and if you're thinking long term storage options you always have things like nas and das (thunderbolt/usb3) units to fall back on.
