It sounds like your current system is already some 8 years old. At this point, architecture has evolved enough that with each part you replace, you essentially create a new bottle neck.
You might look at buying a whole new PC, or something of more modern architecture.
As for value, AMD graphics cards currently offer the best value. Nvidia is riding the AI train and is grossly overpricing its cards.
I am running an RTX 2060 and the sim is struggling (triple FHD).
Unless you can fetch a used Nvidia card at a great deal, you might to look to AMD.