We're talking a DDR3 system, so you will not be able to reuse memory for a new PC. So I'd not overspend, but 16GB is perfectly reasonable. 32 is a bit overkill for a 4770K. Better to save that money for a real upgrade eventually.
Ahh yeah, but he said he was going to upgrade soon...
So on his new system upgrade i was recommending he go past 16gb and jump onto 32gb+
As for the DDR3, system, i wouldn't invest in anymore on it unless he intends to recycle it for something else.
Its done and finished, any additional funds would not merit anything and best to be sidepool'd for the new system.
I really do not think any ram ugprade at this point will benefit him at all.
Diablo 2 Resurection, can use 8GB+ of ram, however, an additional 8 gigs isn't very cost effective.
Its not a complex game like Amazon's New World.
20-30 google tabs is wash on 8gb ram... here i have 62 tabs open and you can see the mem usage.
Is the OP going to have 20-30tabs open and play D2R at the same time? Well, then i would hurry and go for that system upgrade, as the core parts are not that overpriced... *just avoid newegg*
My advice ultimately is this:
A larger SSD upgrade would be preferred, or even a nVME with a PCI-E card adapter if he has the pci-e ports available, or just a large 2TB SATA SSD, to bring with him on the next build as a secondary drive for the new system.
Whatever he spends i would look at the possibility to bring to his new system.