CD players with variable output/volume control

many Wadia models available

Add the Cary 303/200 and 303/300 to your list. The 303/200 goes for around $1500-1700 used here on Audiogon. I own both units and they can run direct to the amp. I prefer the functions of the new remote, though the older remote is impressive in itself as a massive piece of high-end metal.

As for sound, in my system I preferred the 303/200 through my ARC tube preamp, though direct is also very good. The 303/300 gives you the option of switching between a tube or SS output section on the fly and at this point in my current setup, I favor the unit direct to the amp with the tube output.

Do a search, this is one of the single most popular subjects over the last 2-3 years, you'll find tons of info.