The realistic price of an Audio Research Ref should be somewhere around $5000. This Ref 110 looks far to good to be true. I would not buy something From another country to start. It was probably not set up for the electrical requirements here in the US. It could very well be 220v and not 110v.
I also would not pay $4000. for a VT100 mk3. That seems way to high. I sold my VT100 a few years ago for around 3000. Good luck!