CD Player with the best Built-in Volume Control...

I would say, that it is silly to select a CD player, just
because of it's volume control. I have added high quality
volume controls, to several different CD players, and power
amps. I highly recommend the "ladder" style.

I don't know what your budget is, but I use a dCS P8i into Watt/Puppy 7s.

Raysonic 168 variable tube out is soooo good I eliminated my $4K preamp

I think you would find the DCS p8i mechanical if compared to the Capitole M2 se.

I have used both. While the P8i SACD player has amazing detail and leading edge information, the sweetness and smoothness of the AA Capitole will seduce you. If you like the more analogue sound, the AA capitole is the one to go for.

To go the DCS route you need to go further up the line. They make amazing players, but there must be no compromising in your system to to get the best out of them.

Better late than never - for those doing research for current day purchases:

I've owned many of the digital systems mentioned within the various responses. Additionally, I have owned Pass Labs amps (Alephs + a 150.5) and have owned Wilson speakers (Cub, W/P 3/2, W/P 5.1, Duettes).

DCS into the amp and into the Wilson speakers is very, very good. I have to assume that since you own Wilson speakers you want a detailed, forward sound (even though the Sofia are a bit less forward than the W/P).

The AA Capitole and will seduce you, it is beautiful, full, bloomy, bloated in the bass by comparison, very, very warm sounding and lacks some detail as a result. This is typically a CDP that is contrary to what many Wilson owners are looking for. It is a great additional CDP, but this warmth may wear/bore on you over time. Also, you may want to buy two for when it will inevitably be in the shop for repairs - in France were they work very sloooooowly. I have one in the closet that needs to be serviced for the second time now. Replaced the entire Stars system and tubes the first time.

The RA 21 is only special with the GNSC mods, then it is quite good for the used price, but in a different league vs. the DCS, EMM Labs or AA units.

If you want detail then I would add Esoteric and Wadia for the forward sounding wants.

For the neutral minded, I would include EMM and DCS and possibly (but at a noticeable step down) the RA 21 GNSC'd.

For warmth I would include the AA (probably two units to be safe) or better yet, the AMR units. I would tend to skip the BAT or Cary in this category as vs. the AA and AMR you get a more stereotypical tube warmth with a much more notable loss of definition.

This is all just in my opinion. I have owned every brand/model referenced except the BAT and Cary which I have auditioned several times.