I had been running a pi2 as my home router/firewall for the last year and I loved it. I used Arch, so I enjoyed reading about your use of CentOS. Very happy with how far the pi ecosystem has come in a few short years!
However, I was recently upgraded to TWC Maxx which gives me 300Mb downstream. This meant my pi2 was now a bottleneck since pi's ethernet is limited to 100Mb. D'oh! Even if you add on two gigabit dongles and don't use the built-in ethernet, pi2 & pi3 only have USB2 which is shared among all USB, so total bandwidth is limited to theoretical max 480Mbit, and I never saw more than about ~280Mbit in real-world testing.
Also, as a router, it has to pull data in the public interface and send it out private, so the effective throughput is half of whatever your bus is capable of. My 300Mbit was being bottlenecked by my pi2 to only ~140Mbit or so. :(
If your internet connection is 100Mbit or less, then the pi is a great choice. If you have more bandwidth than 100Mbit but still like the idea of a small RM-based router, then the odroid-xu4 is your ticket: native gigabit and also USB3, so that your gigabit dongles can run full speed also. That's what I'm using now and after replacing the loud stock fan with a passive cooler, I'm very happy with it as my new internet router/firewall.