@deep_333 "It isn’t the greatest thing that happened to hifi since sliced bread.".
Agree while it’s not the only option, many of us own both options, and simply insert and remove a good preamp in the system, and hear the engaging difference, likely more so [in a purpose-built "separates" designed system].
Then, insert a good streamer or combined DAC-preamp with a well designed volume control, and one can usually hear the difference yet again.
There are manufactures with good integrated amps, built in preamps and DACs, that sound really nice [with no separates], and usually comes at a hefty price.
Seems like some of the all-in-one integrated units are starting to take over more, and sorta looks to the new future path as old receivers were in the day. The more that show up, creates compensation, and price wars with competition is good to have. I’ll be on the lookout myself for the best sounding value all-in-one integrated when it gets here! Not too far off one can suspect :)