Upgrade Question

There are definite advantages to sticking with the one-box solution.
The next question is budget.
There are excellent one-box CD players out there, actually quite a lot.  The Marantz Ruby and SA-10, Bryston BCD-3, anything from Luxman or Accuphase, the Esoteric models, and the list goes on.

If you like the sound you're getting now stick with Delta Sigma DACs and avoid these 2R2 contraptions.

By that logic we should never try anything new if we like what we have now.  Ignorance is bliss, right?  Many who have tried R2R DACs much prefer them to their previous Delta Sigma DACs, so as usual it comes down to personal preference but no way to know unless you at least try.  Burying your head in the sand is a lot easier though — I’ll give you that. 

The OP said he "loves" the sound of his CDP. It uses a Delta Sigma DAC. Hence my suggestion. What continues to gripe me is how the hell does anyone know what I have tried? Yeah I've heard these NOS R2R distortion generators. 

There are plenty of different chips and different implementations in the CD players, and more in others.  One certainly doesn't have to go outside the one-box solution to sample (no pun intended) a wide palette of sonic flavors (mixed metaphor intended). 

What continues to gripe me is how the hell does anyone know what I have tried?

Nobody cares what you have or haven’t tried — this is not about you.  The OP has had the same CD player for 17 years and just because he loves what he hears now doesn’t mean he can’t love something else even more, especially after 17 years!  How would he possibly know unless he at least tries newer things?  Telling the OP to to “stick with Delta Sigma DACs and avoid these 2R2 contraptions” is discouraging him from trying more recent technology.  After that amount of time, and particularly in the digital realm, that advice is closed minded and potentially counterproductive to the OP potentially finding something he may love even more than what he has now.