It’s certainly an interesting question.
Would a $30,000 integrated sound better than a $1,000 amp and a $1,000 preamp. Well I hope so and it better.
Would a $10,000 integrated sound better than a $5,000 amp and a $5,000 preamp? Maybe. I’m sure there are some nice integrated amps at that price point.
The other issue with separates is compatibility. Will they work well with each other? Hopefully but you never know. With an integrated you shouldn’t have that issue.