While some of those may make good workstations still. They wouldn't make great gaming computers. The speed per core is too low. Most games the speed of a few cores is more important than a large number of cores.
The ones you are looking at with a GTX 1080 run about $1,800. An $1800 price in new hardware would get something which would run rings around the Z820 in gaming VR or otherwise.
Also why buy a GTX 1080? Are you getting a good deal? Looking at current prices. An RTX 2070 is cheaper and faster. An RTX 2080 runs the same price and is considerably faster.
Here is a custom build I specked out on CyberPowerPC. It would outperform those Z820 in gaming by a wide margin. The link is only good for a few days as part availability and pricing changes a lot. You can do a lot of customizing and their prices are generally reasonable. My only gripe is lack of heavy duty air cooling and few non-RGB options. All the kiddies want RGB and liquid cooling.
http://www.cyberpowerpc.com/saved/1LJUWR
- Ryzen 7 2700x
- ASRock X470 Taichi motherboard
- GeForce RTX 2070 (faster than a 1080)
- 16GB DDR3 3200mhz
- 1TB Corsair SP1 NVMe SSD
- Air Cooled (I don't trust liquid cooling)
- InWin Case
- 3x Corsair SP120 RGB case fans
- Windows 10
- 750W Corsair RM series PSU (these get top marks on Johnnyguru)
- Windows 10 Pro
- $1,783
DIY would get you more for your money. I get the feeling you don't want to build it yourself.
Ignore cheap CyberPowerPC systems on Newegg. Those are junk models with the cheapest parts. The custom builds are much nicer. As you can choose all high quality parts.