SLI in Lenovo y510p Worth it?

So I bought a Lenovo y510p a while ago with out the 2 graphics cards. It only came with the Nvidia Geforce 755m card, I was looking on lenovos site and they had the second card for $100 so I figured thats the cheapest id probably get it for so I ordered it, I'm just wondering is it worth the money and how much of a proformance gain would I see. Right now i run games easily high to ultra so would I basically be future proofing by getting the SLI card?