I can't speak to Amplifi as I've just heard about it a few moments ago, but I second the UniFi AC Pros. Long story short, the 2.4ghz spectrum where I live is saturated, and the 5ghz spectrum is wide open. 2 APs, a Cloud Key, and a PoE switch later and I have full 5ghz coverage on both floors. I can bury the capacity with file transfers, BitTorrent, Netflix, etc and it doesn't skip a beat.
The bad news is if you're used to the cost of consumer gear, this ain't it. When it was all said and done it set me back $400. Throw in the cost of a pfSense router (because my old workhorse died recently) and we're at about $600. So, much like everything else, getting to that first 90% is cheap. That last 10%, not so much.
I have a UAP-AC-Pro and a second UAP-AC as an extender, and they're great. But I ordered an AmpliFi HD anyway because it will probably be easier to maintain and I'm interested in the mesh networking. I'm hoping it lives up to expectations.
The bad news is if you're used to the cost of consumer gear, this ain't it. When it was all said and done it set me back $400. Throw in the cost of a pfSense router (because my old workhorse died recently) and we're at about $600. So, much like everything else, getting to that first 90% is cheap. That last 10%, not so much.