Is PhD an overkill?

I work in business and mainly deal with quant finance and statistics + do a lot of programming to implement ideas from quant finance and statistics. I have a master of science in economics.

My problem is: whenever I am trying to dig deeper (by reading articles from scientific journals) to understand some theoretical foundations of a certain idea from statistics and quant finance (ranging from pricing of exotic options to kriging based methods) to modify and customize this idea for my situation, I discover that my knowledge of math is not enough to penetrate deeper in a subject.

Is it a sign that I need to get a PhD in quant finance/ statistics/ math or it would be an overkill and I better go for a less time consuming (bloody) option (if there is any)?