Bletchley Park Lv 1
4 clients in 8 Gigabyte is on the edge, I would recommend more RAM. I unfortunately do not have enough knowledge of Macs to tell you how to switch off the disk swapping (virtual memory system) because that is what makes the system very very slow, it swaps programs and data out from memory to disk and back. 16 or more Gb is recommendable. You may also not have more CPU cores to handle work so that could be a limiting factor.