Wow, thanks for the massive amounts of information folks, truly.
A couple question though.
1. If I Install an older version and root using towelroot...
Would I be able to keep my device up to date with the performance updates Samsung releases?
2. These custom recoveries/kernels that would trip Knox? What do they mean and what advantages do they have?
The reason I chose to use the root method that tripped knox is I knew I was going to flash a custom rom later on. I would really recommend flashing the CM11 rom in the forum. If you wait a few days, most if not all the bugs will be ironed out and it'll be just as stable as stock.
As to what they mean, recoveries are what you use to flash and backup roms (they can be used for more, but this is what most people use) and kernels would just add MUCH more control over the inner workings of the phone (performance, screen calibration, button tweaks, etc).