Dan and I have directly A/B'd his four chassis Doshi Alaap (phono power supplies, phono circuits, line power supplies, line circuits) with my two chassis one (power supplies, integrated phono+line circuits).
Of course the Alaap's phono and line stages are designed to work together. As Raul pointed out, the most careful matching between gain stages is critical and I believe the Alaap's audio circuits are essentially identical whether placed in one chassis or two. I guess that makes our comparison useful for this thread, since the only difference is the room for extra power supplies.
Dan's was being delivered that very day by Nick so, being brand new and sounding it, subtle comparisons weren't possible. With that caveat, Dan's extra power supplies did provide an increase in dynamic headroom and weight. It wasn't a huge improvement but it was certainly audible.
For those who haven't heard an Alaap that marked an impressive achievement, since even a two chassis Alaap has dynamic headroom which meets or exceeds anything else we've heard. After four years the damn thing can still shock me with its startling leaps from silence to a wall shaking first impact - and Dan's is stronger. Kinda scary. :-)
The choice of interconnects can have an effect with separates, obviously, but it wouldn't necessarily be a negative effect. What if a separates owner chooses wire that's better than what's used in the integrated version? The results could actually be better. That may be unlikely at the level of a Doshi or Raul's Essential, where every component including wire is specified to the max, but in lower performing units it could easily happen. Drop a set of Nordost Odins between two $1K separates and watch what happens. Foolish? Maybe, but probably a big improvement.
Summary: for the Doshi design, four separate chassis provides some increase in an already amazing level of headroom with no downside we could hear, at least not through the newness of the separates. For other designs, who knows? Implementation is everything, here as everywhere.
