I've bought new parts and I am awaiting their arrival so I can build my brand new computer. I've decided to go for Arch Linux with KDE plasma or perhaps Gnome as my desktop environment but that's as far as I've come.
If you're installing Arch, one trick the installation wiki article doesn't tell you:
If you type "archinstall", it has a command line installer there that'll do the install for you, and lets you pick from several desktop environments as well. I've had it crash before more than once, so it's not perfect, but it's less of a pain then doing it all by hand...