I would be scared to death to buy a used piece of tube equipment. It's very very difficult to get it serviced and then once they have it and because talent to deal with tube gear is very very limited you may wait months to get it back. Not sure about the health of audio research financially. I looked at the reference 10 but that was very expensive but I liked the separate power box. But they do use lots of tubes and they run the tubes very hard from what I hear. Not the best piece of equipment for a home theatre integration which is what I wanted. Although, I just use the AV processor during the day for listening on a centre channel with surrounds and bypass need to turn on the tube pre-amplifier I have until at night so Tube use may not be as bad as I originally thought it might be. Plus I invested in nos tubes with the hope that they will last forever. For example jj tubes Will likely go bad very quickly and then they begin to crackle and then you gotta figure out which one is bad so transitioning to NOS tubes may be good for audio research gear although I don't know.
If it all possible especially for preamplifier I would stretch to buy something new. Especially tube gear. McIntosh solid state is a good used but tubes again I would lean toward buying new if it all possible saving a few thousand dollars in the longer run may not be a worthwhile thing to do and will always weigh upon your soul.
I bought a tube amplifier new and thankfully the dealer was incredibly accommodative because it had issues that were resolved and I'm not sure used gear would've afforded the same level of service. Although the dealer was very good so if you're gonna buy something used go through a dealer.
