NUKEMDUKEM

Honestly the 2400g should be good till ryzen 2 comes out next spring, overclock it as far as you can and make sure you have good memory. Performance should be just fine even in slightly cpu bottlenecked titles I'm using a 2600k with a 1070 ti and I haven't had a problem.

Full dos game all u need is the doom wad file.
 
Get brutal doom and gzdoom or Zandronum 
 
You good to go. Look on youtube how to run brutal doom.
 
https://replayers.org/abandonware/ultimate-doom-dos/
 
Full game of ultimate doom (aka original with extra content)
 
https://gamesnostalgia.com/en/game/doom-ii_#download-section
 
Full game of doom 2

Why would u get shareware when the full dos game is abandonware In my above post. Lol they dont make the dos version anymore and all u need is the doom wad file to play brutal doom mod/gzdoom/zandronum

Dont bother with either wait untill 2nd gen turing chips or new amd.

Quality modern FPS that you will be able to run excellent on that rig:
 
DOOM 2016 (by faaaaaaaaar the best of these)
Prey (super good)
Far Cry 5
Battlefield 1
Outlast 2 (horror first person game)
Dying Light Bad Blood (melee battle royale with zombies) 
Overwatch
Quake Champions (hardcore multiplayer game, but really good)
 
You can get all these games for super cheap, especially if you go gray markets.