Can you give the figure in Activity monitor/memory after you had "stuttering and skipping."
Put 8 core in VEPRO setting and Pre-load buffer to normal in Directory Manager
Put DP with 1024 and test if it is playing ok, if not put pre-load buffer to bigger (you must re-launch VSL each time you change a parameter)
see : You disable all non needed (Wifi, Bluetooth, Flash ......)
Reboot, do not lauch any softare, only VSL and DAW
To see if you have enough CPU power and enough fast disk you should set all pre-load buffer size to maximum (in you DAW and in VSL)
Is there are no more problems, you can start to reduce them until you get problems ! and set it back to the values where there is no problem.
Then if the latency is not acceptable, you should go with SSD and/or put memory to 32 or 48 GB, and/or change computer, and/or add slaves
For Kontakt it is the same, also it is better to have Kontakt in the DAW, if you put it in VEP you will add another layer in the processing.