I just bought a new PC.
i5 processor
16GB RAM (2600mhz)
4GB graphics card
500GB SSD
2 x 2TB HDD
Getting a PC which has the programmes and operating sytem on a Solid State hard drive will be beneficial. Keep the photographs on a normal HDD, preferably 7200 rpm.
The main interface is the monitor of course. To utilise a good monitor you do need a good graphics card and not the shared graphics built into the mother board as that usually uses the main system RAM, hence "shared".
My main monitor is a Dell UP3017, I think that's the model, which has 98% of the Adobe colour gamut. This does give a better rendition of colour. My second monitor is a Dell Ultrasharp 24" (not 4k though) so there is a decent comparison, side by side. If you get a large primary monitor you really don't need a second one. Depending on how close you sit you may not need that large a screen.