Audio Research Amp/Pre matching

It is time to once again upgrade(change) my system. Looking at building a new system around a ARC VT100 amp, question is which ARC pre amp is a good match for this amp. And I am certain that a REF 5 would sound great but I mean a older good value for the money ARC pre that is a good blend with this amp.
Thank you for your suggestions
I had an Audio Research VT100 matched with an Audio Research LS 25 preamp in a previous system and it was an excellent match.
Go with a REF3 or and LS26, I have the LS26 and would like to upgrade to the REF3 when the $$$ matches the dream. Also
ARC is doing some upgrades to the REF3 , I assume the knowledge they gained in producing the REF5 has revealed some circuitry/components that they can retrofit. A very nice gesture that ALL manufactures should offer.