I own both the Rotel RCD971 and the Marantz SA8003 and I think you would have to pick a Marantz player at this level or higher (the higher end players being designed by Ken Ishiwata) to see any improvement over the Rotel RCD971.
The Rotel still sounds more dynamic and exciting than the Marantz player but the Marantz player has the Rotel beat when it comes to timbral accuracy and sheer musical realism, so a choice between the Rotel and Marantz players will very much come down to your musical priorities.
All the higher end Marantz players exhibit the refined, "audiophile" sound that's the hallmark of Ken Ishiwata but I would agree that the lower end players (such as the CD5003) would compare poorly to what you already have.
The Rotel still sounds more dynamic and exciting than the Marantz player but the Marantz player has the Rotel beat when it comes to timbral accuracy and sheer musical realism, so a choice between the Rotel and Marantz players will very much come down to your musical priorities.
All the higher end Marantz players exhibit the refined, "audiophile" sound that's the hallmark of Ken Ishiwata but I would agree that the lower end players (such as the CD5003) would compare poorly to what you already have.