.. nice gaming machine: fully equiped, everything is already "on-board", nothing to add.
I think the GTX 860M has still enough power even for the latest games...
my second gaming laptop (msi GE60-2PE) has similar equpment:
GTX 860M, i7, SSD 256GB (crucial M500), HDD 500 GB, display 15 inch....
Intel® Core™ i5-4210H Processor (3M Cache, up to 3.50 GHz) quick reference with specifications, features, and technologies.
www.intel.com
Making sure your ram works in dual channel (2 x8 = 16GB) let's everything run just a bit more fluent.
An SSD as bootdisk is also highly recommended.
For both upgrades it is difficult to say how much faster things are, but you will absolutely notice them.
Added a PQI My Lockey usb fingerprint reader for Windows Hello.
Love the large (17,3") matte IPS display and the backlit keyboard.
Those are things I would look for should I buy another laptop.