What kind of upgrades would I need to play DCS maxed out you reckon? Any ideas? I probably won't invest any more money in this rig, but I would like to see what it would cost just for the heck of it.  
Brother has the same CPU you bought, fast SSD and 128GB memory also. He has an RTX 4090 and a PIMAX Crystal. He cannot max everything out but is very happy with the settings he can run.
He also has an HP Reverb G2 and will use that on his old machine for grandkids and guests. It stopped working when Microsoft dropped WMR. I thought we had it going again with the Oasis driver. All other VR games work but not DCS. He brought it over and we thought we had it going but we didn't test it enough. It will work as it does for other people so I just need to get him to bring it over again so we can test a fresh windows install.
So, the fastest you'll get is an RTX 5090. Even that probably won't be perfectly smooth in DCS with max settings on a PIMAX Crystal or higher.