Used Audio Research PH8 plus or minus. I have owned a PH2, PH2SE, PH3, PH8, and REF 3, REF3SE. The gains were huge until the PH8. To me the PH8 is the minimum standard to get the phonostage out of the way.
After over 30 of having an Audio Research preamp and/or phono stage I would buy nothing else. Also, Audio Research sounds better the more Audio Research you own, it is highly synergistic.
Buy the most recent ARC phono stage you can get. I would entertain nothing else since you already have a VSi75.
I have auditioned the ARC I-50, VSi75, LS28SE, and VT80 extensively over the last few months… the last two were just purchased by a friend of mine. You can see my ARC main system under my ID.