I just picked up a new PC, mainly for astro work such as Photoshop CC and running Nebulosity, Deep Sky Stacker and Registax. I had considered building my own computer but for the price of the individual components it was hard to beat a new Dell XPS 8700 with a warranty. It runs Windows 8.1.
The first thing I did was install Start 8 to get the Windows key back
. I got a Core i7 with 16GB of ram, a 32GB cache and a 2GB graphics card. The 2TB disk drive is lightening fast and opens Photoshop CC in a few seconds-rivalling an SSD. I can upgrade the ram to 32GB if required but I would recommend at least 12-16GB for Photoshop.
I have been using Windows 8 for over a year now and find it very stable and without any compatibility issues.