I am not quite sure buying a used CJ pre-amp is a worth even a mint one. What are you really getting for your money?? Most CJ pre-amps and line stages have no remote, headphone jack ( or amp) and no phono stage. Sure, if you want the purest sound, a no-feature line stage "may' be great.. Of the above features, the headphone feature may be most optional..
However, it you are still doing analog and a have quality set-up, you have to purchase an outboard phono stage which could run as much as $500 possibly more. (Unless you can find a used mint Musical Surrounding Phonnom II which can be had for about $350. Also an additional IC must be purchased that is almost audiophile level.
The volume control I always considered as a type of tone control which allows the listener to adjust levels incrementally until you have reached a volume compatible with the dynamics of the recording Therefore, it is easier and more enjoyable to do this from your listening position than getting up every 5-10 minutes to adjust volume as you from track to track on a CD or LP
I had a CJ PV-8 in 1988, and in retrospect, I was happy it had a MM phono stage; I took it for granted that it was more than adequate quality, and I played a 80% LP's in those days, and only 20% CD's It sounded good, but I was somewhat uninformed about the differences in sound quality between phono stages.. That is my 2 cents. Good Luck