Looking for an opinion on routers I currently run a ASUS RT-AC68U w/ Asuswrt-Merlin firmware (384.13). My home connection is a 100/40 fibre to the home setup, in a two story rental townhouse. 

I'm finding as more and more devices in my home are depending on wireless, my current router isn't feeling totally up to the task. I have roughly 20 clients on the network (TV, consoles, phones, smart devices etc) and I'm getting a bit of slowdown now. I've been doing a bit of reading online and I'm finding Ubiquiti to be well reviewed, in particular the Ubiquiti AmpliFi High Density HD Wifi Router. Speed and stability are my biggest priorities, however I also a degree of control over my network (port forwarding, QOS, custom DNS etc). Would this device be an upgrade on my current setup, or would it be more of a parallel upgrade?