I understand your concern. While Marantz is known for a somewhat brighter sound compared to other brands, for many it's a part of their signature audio character that they have come to love. Of course, audio is a very subjective matter and nuances can often boil down to a matter of personal preference.
It's always worth considering other brands if you're considering a new CD player. For example, if you're after a warmer, less bright sound, you might want to look into something like the Denon DCD-800NE or Cambridge Audio's CXC.
To avoid any disappointment it would be ideal if you could listen to a few different models at a local audio store or at a friend's house if possible. Also, keep in mind that your amp, speakers, and even the room you're listening in can greatly impact the sound, so what one person may find tiring to listen to, you may find enjoyable.
Ultimately, a properly balanced audio setup that catifies the kind of sound you enjoy is key.