Update:
I am keeping the Marantz CD5001 CD player and returning the CD5003 back to Crutchfield.
The 5003 is simply a little TOO laid-back, and a little too dark for my own personal tastes.
The headphone jack on the CD5001 also seems to have a little more output than the one on the 5003.
While I did like the CD5003, the 5001 suits my tastes and headphones better with its livelier, brighter, and more energetic personality.
It is a little rougher around the edges, and less refined than the 5003, but it is more involving and fun for me and my tastes than the 5003.
The 5003 sounds alittle "too refined", if that makes sense?
Again, this is using Sennheiser HD-650's, exclusively.
But, if you own brighter and more forward cans such as the AKG K701's, Grado's, or Beyer Dynamics, etc., or a brighter amp, the 5003 may just be the ticket for you!
I do recommend giving it "a spin", if you know what I mean.
Now, I want to compare the upcoming SA8003 and the CD5001!