I totally get why a custom unit might be a lot better than a built in unit. I had never before pondered the possible need for one.
I guess most self contained kit is built to a budget or has size constraints, all manner of compromises being made. So anything built as a dedicated unit should sound better.
However, then of course you get into the sticky mud of this thread, is it better or just different, well mostly they will of course all sound slightly, or wildly, different to each other, but which do you prefer.
Then of course, if I have a DAC, and it sounds great, it could make my vinyl collection redundant... something else that puts me off seems to be the typical digital issue of changing specs and standards DSD64, DSD128 and no doubt 256 and 1K etc to come..? Bit rates and frequencies rising in an effort to make a digital signal closer to the analogue original (assuming that's what it was)... It reminds me of the early computer days the endless upgrades, rebuilds etc...
Is it not the equivalent of a comb-over?