Hey there,
Although your system is a little dated, it's still very relevant IMO.
With a little OC on your CPU, it's a very capable gaming CPU still, and suited to VR. The RX480 is a little on the light side. Getting the GTX1080 would be a good fit with your system, and with said OC on the CPU, should drive the GTX1080 pretty nicely.
Make sure you have a good PSU. What is your current one. A GTX1080 can hit 200-250w on it's boost clocks, and although it's not a crazy amount more than the RX480, it's worth thinking about.
You can try your system on a VR test, and see how it pans out. It will give you a rating and you could gauge things from there.
Like the Steam VR test ...