GTX 780 SLI or 1x GTX 780 + GTX 2080

[Gabriel]

Hello there, i am in a dilemma and hopefully some of you guys have been in the same position or tried to do the same thing. 
The Story: I was running 2 780's in SLI hooked up to  4 monitors 2x 1080p@144hz and 2x 1080p@60hz.

Sadly my 780 has decided to give up on this world and all of its 3-dimensional glory. I still have one working 780, but it can't run 4 monitors and i really need to be able to run 4 monitors. 
I found a guy selling an old 780 on eBay. This will allow me to run my old setup again and it worked perfectly fine, however, should I instead get a 2080 and run 3 monitors on the 780 and use my main monitor and gaming on the 2080?

 

I have this dilemma because on one hand i have seen how powerful SLI is and on the other hand I know that 2080 is also quite powerful. I Don't what to do, any suggestions? 
Thanks and any help is appreciated  

[Fasauceome]

the 2080 will easily outpace the 780s in SLI even with 100% scaling, but if the SLI setup worked for you then you should go with it because it's a ton cheaper.

[Glenwing]

GTX 780 SLI is about equivalent to a GTX 1070 or 1080. RTX 2080 will be a fair bit more powerful.

[FloRolf]

Why would you still install the 780 with a 2080? It can easily run 4 screens iirc with almost no performance hit.