Speaker/amp setup for new apartment

[abs_rio]

Hi everyone! Would appreciate some advice please. I have a friend who has moved into a new flat. He has a large open plan living area where he would like to install speakers connected to a 4K television. He prefers the minimalist look so his electrician has advised him to go for a Denon Amp with 4 Monitor Audio ceiling speakers. Am I right in saying that without a soundbar/front facing speakers he would not get adequate surround sound when watching a movie?
Thanks in advance.

 

[abs_rio]

He seems set on using ceiling speakers and/or soundbar. Would he need more ceiling speakers with the Denon Amp to get decent surround sound? Or is better off adding a Sonos playbar to the ceiling speaker setup?

 

[abs_rio]

Thank you lucid, really appreciate that. It's very informative. I did mention in-wall speakers to him but he's doing a full refurb of the place and hasn't decided where he will position his TV and sofa exactly. With the Sonos Playbar my understanding is that he would have to use the Sonos CONNECT:AMP to drive ceiling speakers to act as rears surrounds? The Sonos SUB could also be linked to the system.