Those GPUs, even in 4x SLI, will not meet the minimum GPU requirements of today's games as they only have 1GB VRAM. Your only hope would be to extremely turn down resolution and quality settings to run VR. It's the old classic "you wanna play, you gotta pay" scenario with PC gaming. Battlefield 1's minimum GPU requirement for example is a 2GB GTX 660.
And speaking of 4x SLI, that third and fourth GPU would see severe diminished returns in increased FPS. At best, the typical 3-way SLI only boosts FPS by 25% and the fourth GPU by a mere 10%. And that's for games that scale well with SLI...not all do.