The salesman may just have been selling, but I it sounds like he was actually following the sound and widely recommended philosophy, "the source must come first". Quite simply, the best speaker in the world - whatever that is - cannot reproduce what isn't fed into it in the first place.
If you start at the back end by upgrading speakers first you risk two problems. First, revealing speakers might highlight the shortcomings of inferior components or wire earlier in the chain. Second, choosing the "best" speakers depends on what amp you'll be using. You can't choose an amp without knowing what preamp will feed it. You can't choose a preamp without knowing what source(s) will feed IT, etc. You get the idea.
Starting at the source and upgrading in the same direction as the signal path makes it easier to match components effectively and avoid expensive errors. As far as what you hear or don't hear between these particular CDP's, I'll defer to those who have more experience with your particular components.
