Reviewmeta gives it a passing grade....so I guess it depends on what algorithms you are using.
The K3c is currently available from various vendors on Amazon/Ebay for less than $60. (The K3 about the same). I have not tried a K3c, but I have owned a K3 for 3 months now, bought because of the well below $100 price. Using the most recent stock firmware, it has been the fastest and most stable router I have tried. Previously I several Linksys routers that needed weekly reboots.
My use case is simple...I have a lot of streaming devices in a small apartment. But for someone who has simple needs...setup was easy/trouble free. I consistently get the full 250 MBS Comcast that I pay for.
My point is, the firmware would certainly be a major negative to anyone who wants features it does not support (and there are a lot it does not). I am pretty sure most readers of SNB forums are in the sophisticated user category.
But, it has worked great for me and I just ordered a K3c for a neighbor with similar needs cause $40 is worth a try for the #3 rated router.