I5 3570k says to be powerful enough for VR, however I would suggest getting a 1060 if you're only looking for gaming/VR and then keeping your I5. Or get a 1070 and save money from buying a new i5 for future upgrades.
I would suggest better graphics if you want to futureproof it for so long. There is many options in same pricerange with 6th gen I5, 960M, 16GB and so on...
Monitor your temperatures and compare them to others with same specs to see if yours are higher than normal. Also update graphic drivers to see if that helps.