I have often been challenged with the same question. I have and love the VAC 70/70 but that isn't relevant to your question. IMO, it ultimately depends on your input source (and how many) , but I lean towards having one than not. A preamp removes the raw sound, provides coherence and helps with the imaging I have found. My input source is Sonos and I have tried with/without a pre and always go back to the pre. It's easier on the ears and simply brings everything together. My pre is a First Sound tube pre and whereas not all preamps are the same, I would still prefer one in my system for the reasons I mentioned.
Goodluck
Goodluck