Little known fact, the 802.11ac your fancy wireless router includes only works in the 5 GHz band. The 2.4 GHz band does not support 802.11ac and defaults back to 802.11n.
What does that mean?
You will only possibly experience the max advertised speeds less than 100 feet away in your home. Add walls and other objects and that will greatly reduce. The bigger antenna is not going to help all that much, as the antenna in your mobile device is tiny and WiFi is a two-way game.
What about this new 802.11ax?
It does not increase the throughput (speed), as it focuses on efficiency. Instead of making the channels larger to push more data, 802.11ax subdivides the channels to use them more efficiently while not introducing interference as wider channels can do. And guess what? 802.11ax works on both 2.4 GHz and 5 GHz.
So, the best thing to do is buy a decent wireless router and do not focus on speed but focus on consistent data transfer. Consistency is way more important than raw throughput.
If you do want consistent 802.11ac speeds throughout your home, look into wireless mesh systems as they are designed to do just that.