For a "large room", the key would be your seating distance and desired SPL. Unless you sit quite close such as less than 3.5 meters, have sensitive, easy to drive speakers and happy with moderately loud spl, you probably should get such an integrated streamer/amp that has preamp outputs for future proofing.
Unless your room is well treated and have favorable geometrical features, room correction is the best bang for better sound quality. Between KEF and Wharfedale, I have more faith in KEF, but only their R series and the reference series. Most of those will need competent power amplifiers that most streamers like will fall short.
In my opinion, if you have the room, I would go separate, integrated solutions are of course great for many applications where space, aesthetic, ergonomics are the limiting factors, otherwise...
(hint: may as well stick with just an AVR, there won't be sound quality issues if you choose wisely).