Audio Research pro's-what pre-amp to choose?

I am trying to match up with my Mesa Baron and any speaker I might get in future.If I was looking at an AR on the used market for $2000 or less which of the myriad of models would you reccomend?The tube compliment,balanced or not etc.Seems to quite some choices.
interesting question! i have a mesa baron and fairly neutral speakers. i find the top end of the baron can be a problem with a lot of preamps. i have been usng an arc sp10 with good results. i use 6h23eb's in the line stage of the sp10 and yugo el12ax7's in the baron. this gets me a nice silky top end - very detailed but not etched.
that's easy

ARC LS 5 - all balanced but you can use cheater plugs from ARC or Radio Shack.

I had an LS2 and the ARC LS 5 beats all the other arc preamps except the ref 2

I've owned the SP-6B and the SP-14. The 14 is an
outstanding preamp with a particularly delicious
phono section. It is also very versatile with a
myriad of switching options. It can be had for
$900-1200 in excellent condition.

A friend owns an SP-11 MK II which he believes is
the finest preamp they ever made, though it often
sells for >$2000.

Do you need a phono pre-amp? If not, restrict your search to the AR linestages (model numbers bear an LS prefix). Otherwise, you will want ot look at the SP models.

The better AR products seem to all have balanced design. In your price range, you can look at the LS15, LS16, and LS22. My understanding is that the LS5 MkIII is one of the best linestages that AR has produced. It is, however, more than $2000, and if you are using any single ended sources or amps with it, you will need adaptors (no big deal). Adaptors are not required for the other linestages mentioned. If all your gear is balanced, you can use the LS5MkII also (less than $2000.).