High resolution image manipulation with lots of layers is very RAM intensive, especially if you're doing it in multiple applications at the same time.
Have a look here: http://www.pugetsystems.com/labs/articles/Adobe-Photoshop-CS6-Memory-Optimization-182/page4
A 1GB project file winds up using ~22GB of system memory.
My advise would be to look for an E5-1600 V3 series CPU and a GIGABYTE MW50-SV0 workstation motherboard. Start with at least 2x16GB ( M393A2G40DB0-CPB0 or similar) and add more as needed. With currently available DDR4 the board and CPU together will support up to 128GB memory, eventually it will support up to 512GB with load reduced quad rank 64GB DIMM's.