RAM's bloody expensive ATM isn't it?!!
TBH I don't think you should consider upgrading, yet, as you're getting pretty much everything you can from your current system without bottleneck.
A significant upgrade that you'll really
notice would need an upgrade of Mobo to take advantage of DDR4 and then an upgrade of your GPU, so it's a whole build really.
Might be worth waiting until NVidia releases cards based on the Volta chipset