Auto over clock

Hello! Its been about a week since ive built my newest gaming pc, I have a ryzen 7 2700x on a Aorus Pro b450 MoBo ands so far its looking pretty good but today i Noticed something. Since my CPU Base clock is 3.7 Ghz i saw that it was running at 4 ghz sometimes 3.9. I went into BIOS and checked...

So I've been thinking about SLI'Ing my 760, but my friend says it would be more efficient to just upgrade my CPU instead. My question is, what should I do? Upgrade my cpu, or go for the SLI My current processor is an i5- 4440 3.1GHz