Preamplifier: Yes or NO ?

"yes."
In any case, there are lots of threads in the archives about this. Try a search using multiple words "cd volume control".

"Yes" is my answer also. Search on "passive active" and you will find a long-running discussion of passive vs. active preamps. Passive preamps are pretty close to no preamp at all, they do switching of sources and volume control but don't add gain.

As the saying goes, "the best pre-amp is NO pre-amp."

A good preamp is a good thing if it gets out of the way of the music. The preamps I like are the Rowlands, Levinsons, Audio Research LS15, LS16, LS25, Reference line etc...all great. The Conrad Johnson pre's are also good. Try before you buy though. I find the stage grows in depth and vertical expansion. There isn't more transparency, just growth. There are more good pre's, try all you have access to. The best for the least is the one to get...

It all comes down to the volume control and output of the CDP. A buddy of mine has a Metronome CDP but it has a low end volume control. It sounded very nice until we added a preamp into his system (all preamps gave the same results when we added one) soundstage grew, dynamics grew, etc. That being said, I had the Wadia 861, Resolution Audio Opus 21 and Accuphase 77 in my system. The difference was much less then my friends. Add in the cost of another pair of ICs, power cord, tubes for a tube preamp and well you get the picture. I have not tried the Levinson or Audio Aero Capital CDPs that are supposed to have very good volume controls. I also have not tried a modified CDP with volume such as Modwrigth or APL. These will cost as much as the preamp.

So is a preamp better, that depends on what you feel is better and how much you want to spend. You get what you pay for.

Happy Listening.