Which is the best desktop PC for photo editing?

Paul is looking for a desktop PC to edit his photos in Adobe Lightroom. What sort of specification would be best?

I saw your response to a question about a laptop for a photography student and noted the suggestion that a desktop would be a better option in terms of actual capability, not to mention the ergonomic advantages you've mentioned in previous articles. What specification would you recommend for someone with a mid-range DSLR using Adobe Lightroom for RAW files, but only as a hobby?

Although I think I probably could build my own PC, I'm not sure I want the additional faff and the risk that some components just won't talk to each other properly. On my last desktop, built with a friend, I had never-ending problems with the graphics card, which were only fixed once I replaced it.

When I wrote about the best laptop for photo editing a month ago, several readers asked for advice on desktops. As you already know, you want the fastest processor, the most memory, and the fastest hard drives and SSDs that you can afford. The problem is balancing the different requirements.