Advices for Audio Reseach Reference preamp

Dear members,
I would like to upgrade my Preamp from an Audio Research LS25MKII to a reference series (my budget will allow me to go through a Ref2 or Ref2MKII). My Amplifier is an Audio Research VT200 which is a good match with LS25MKII at the moment.
I wanted to know if a member did this type of upgrade and what are the key benefits ?
Any recommendation regarding Ref2 or Ref2MKII choose will be greatly appreciated
the LS5 is another top contender although it is all balanced inputs (you can use cheater plugs there) and can be had for a bit less - they come up on audiogon from time to time. I'd put it right up there with the Ref 2 (in a blind demo it was neck and neck)

You might also want to consider a Great Northern Sounds upgrade on your existing LS25 or an LS5 or Ref 2
You may also want to consider the LS26 which is better in overall presentation than the Ref2mkII.
I bought my Vandy 5A in Chicago from a dealer who was also a ARC dealer. Later when in the market for a good preamp (got back into vinyl) I talked to the guy who sold me my Vandys. He said the Ref2 was softer than the MkII. Maybe too much so for some systems. I don't know for sure but it seems the MkII came out fairly quickly. I had indicated that I was looking at the Ref used market, he sounded sincere saying all the Ref models were very nice preamps.

I have a Ref2 mkII and while I will likely upgrade to the Ref3 at some point I recently choose to upgrade my cartrage from a ZYX Fuji to the Universe instead.

There is a lot to be said for other ARC models just below the Ref series. But the Refs have bigger power supplies and/or more input/output flexability.