Audio Research SP3-a1

 ARC does not charge excessively for repairs. What did they say was wrong with it? A unit this old may have a number of issues but ARC will go through it with a fine tooth comb. It is worth the cost.

 Has your unit been "modified"? If so ARC will insist on removing the "modifications" before it can be repaired. This is a classic piece, I would not let just anyone work on it.

 That does seem excessive. It has only cost a few hundred dollars both times I sent pieces to ARC. I agree, would put it in the closet. For that kind of money you can get a much better preamp.  The LS2 and LS2 mk2 would not be on my list. I had a LS2B mk2 for a few years in the late 1990's. It was good in it's day but never great.

 I sent my V70 amp to Audio Research some years ago. The amp was almost 20 years old at the time. They did a superb job on it and the inside looked like new. I think they actually cleaned the circuit board. I would not be surprised if they do the same type of thing to your preamp. They want to clean every thing thoroughly and check every connection so it sounds it's best. Let us know what happens when you get it back.