Hi, Bob! Hope to see you again soon.
You are correct that the Cambridge 640C was not available when I got my Music Hall. However, Bill called me once to rave about them, and asked me to come over to give his a listen, as he was selling them. Since then, I have also been on the Cambridge bandwagon, but we both agreed that we preferred the MMF25. The jump (sonics, extension at both frequency extremes, musicality, openness, build, and reliability) Cambridge made from the D500SE to the 640C at the same price point is simply astounding. The D500SE was like a $250 - $350 machine, whereas the 640C is like a $1200 - $1500 machine.
Marty, one recommendation I would like to make to you with the Rega before you look for a new player is to give the HomeGrown Audio Silver Lace interconnect a try. It really ups the ante in terms of what you can get out of a CD player. The music can really become pulse pounding, with a lot more jump and slam. In my experience, it seems to push the sound towards what I have always wanted to fix with the Regas. You may just find that you do not need to move to a new player at that point. Anyway, even if you still move to another player, this IC will continue to serve you well.
Two other CD players I would like to recommend are the Granite 650 and the older version of the Audio Aero Prima.
The Granite keeps the richness of the Planet, and is about is good in terms of weight and heft as one can find without spending silly money. Detail, clarity, and refinement will significantly improve. Whenever I see them used here on Audiogon, the price tags are in the range of maybe $350 - $700. I watch in disbelief when they sometimes languish for weeks. I can personally attest that they will easily compete with players in the $3000 price point.
The older Audio Aero Prima, with 6922 output tube, is just a gnat's eyelash away from the best players you can buy, for under $1000. Rolling that output tube, along with interconnects and the power cord allow one to paint a wide range of sonic pictures. This really is a giant killer!