You don't need multiple GPUs for a multi monitor setup FYI. only if you want to game on multiple monitors. Even then, it's better to go with a 4k or ultrawide monitor these days as opposed to separate monitors (SLI and Crossfire isn't supported very well anymore).
I moved to a 1080Ti and a 3440x1440 ultrawide and it was a good choice for me.
Choices aside, now is a *******REALLY******* bad time to buy a GPU or RAM. The prices are so inflated because of crypto currency miners, the price I got my 1070 for 2 years ago is HALF what it costs now, and my 1080Ti was 500$ cheaper than the current price for them. Wait for GPU supply to increase before buying. For 1080p gaming on a single monitor, wait till the 1070s are back in the $450 range, and for ultrawide/4k gamins, a 1080Ti or possibly 1070Ti is a good choice at 850/750 respectively