Suggestions on used CD Player with Volume Control

I love my Shanling CDT 100, well below $2000, 2nd hand and some money to spare for modding later if you wish

Cary 308 (solid state) or 308T (tube output), both are very good and fit within your budget figure.
Regards,

Keep an eye out for a used Wadia 830. They sell quickly but they're usually around $1800 or so. If you could stretch to about $2500 you might find a used Resolution Audio Opus 21, an excellent player. Also there are occasionally older Accuphase players for around $2K, like the DP-70 or DP-65, not the V versions. Also search the archives as this question has been asked hundreds of times.

Cary 308T.

I would stretch a bit ($2200-$2400) and get a used, latest iteration Resolution Audio Opus 21. This is an excellent player in stock form
Down the road you can get the Great Northern Sound Company mod and have one of the very best Redbook players.
I'm sure the other suggestions are good as well.