PC Upgrades or New Rig

Solution
I'd replace the CPU/MB/RAM now and save up for a better GPU. Then what you get for the old CPU/MB/RAM I'd use to buy a SSD (240gb +) for the OS and maybe a couple of games with really long loading screens.

PCPartPicker part list / Price breakdown by merchant

CPU: Intel - Core i5-8400 2.8GHz 6-Core Processor ($178.89 @ OutletPC)
Motherboard: Gigabyte - B360M DS3H Micro ATX LGA1151 Motherboard ($65.99 @ SuperBiiz)
Memory: GeIL - EVO FORZA 16GB (2 x 8GB) DDR4-2666 Memory ($158.99 @ Newegg)
Total: $403.87
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-05-03 14:03 EDT-0400

WildCard999

Titan
Moderator
I'd replace the CPU/MB/RAM now and save up for a better GPU. Then what you get for the old CPU/MB/RAM I'd use to buy a SSD (240gb +) for the OS and maybe a couple of games with really long loading screens.

PCPartPicker part list / Price breakdown by merchant

CPU: Intel - Core i5-8400 2.8GHz 6-Core Processor ($178.89 @ OutletPC)
Motherboard: Gigabyte - B360M DS3H Micro ATX LGA1151 Motherboard ($65.99 @ SuperBiiz)
Memory: GeIL - EVO FORZA 16GB (2 x 8GB) DDR4-2666 Memory ($158.99 @ Newegg)
Total: $403.87
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-05-03 14:03 EDT-0400
 
Solution
I fully agree with WildCard's option and plan. While the outdated 2GB HD 7870 is not going to do well in today's games, a chipset upgrade is more important. A new GPU on that outdated FX platform will be bottlenecked, especially at 1080p. Intel's Core i5 8400 is better than a comparable Zen (of either generation) at 1080p gaming.

That HD 7870 is not even benchmarked in DX12 games anymore on most tech websites, and in sites that do still compare it in older DX11 games like GTA V and Witcher 3, it shows about equal to a 2GB GTX 1050 in performance. But waiting on a new GPU is a good thing because Nvidia is coming out with their new Volta line of GPUs starting this summer (GTX 11xx or 20xx, however they are going to number the new series).
 

WildCard999

Titan
Moderator
^^Yeah and that's if you don't have a problem overpaying for it currently. And B&H Photo has some killer prices from time to time but they get snapped up quick. Keep an eye on Best Buy and Microcenter GPU sales too that occasionally slide under most people's radar. Most miners and gamers are looking at NewEgg and Amazon. Not long ago Best Buy had a GTX 1070 Ti for $530 (can't remember the brand).