Listen to everything you can. Make a long term plan. Synergy is very important. You can have an excellent sounding piece of equipment, but if it is not a good match for your other pieces. It will just sound mediocre. Also do you want the up keep of a tube amp? There is expense in replacing the output tubes every 2000 to 3000 hours.
Audio Research is some excellent gear. I have owned it since the late 1980's. But like any company some pieces are better than others. The amps made a major change in 1988 with the Classic series. A more modern sounding higher resolution tube amp. These amps can still hold there own against more modern Audio Research tube amps as well as most others. If I was going to choose the best bang for the money ARC amp it would be a Ref 110. An truly excellent sounding amp that can be found used for a really good price. It can run KT120 tubes and has an hours meter. If you don't want to deal with having to replace tubes. I would go with a Pass amp. Some of the best sounding solid state amps I have ever heard.
For a line stage I would go with an LS25 mk2, Ref 2 mk2 or Ref 3. The Ref 5se is significantly better but used would still be twice the price. They will all mate well either either ARC or Pass. A phono preamp really depends on the type of cart. For MM a PH5 is a nice sounding Audio Research phono pre. A PH7 if you are thinking MC. Audio Research has always been known for excellent preamps.
You need to at least listen to Audio Research before making a decision. They make some of the finest sounding gear in the world. I have owned their gear off and on since the late 1980's. I have moved away from them a few times but always ended up coming back after a short time.