What is Audio Researches best preamp period

I have an Arc LS 5 MK II wonderful piece, very engaging
I owned an LS 2 Mk II I could never get things right with it- Jafox here steered me clear of it's brightness
and turned me on to the LS 5 (thanks again) I have heard a few people tamed the LS 2 to some degree with certain tubes (do a search here)

The LS5 is the best bargain in the Arc line, it is all balanced inputs (but you can use cheater plugs) In the direct comparisons I did wit the LS 25 and ref1 the beefier power supply of the LS 5 clearly outshinned them

I haven't had the pleasure of auditioning the Ref3 in my system, nor would I be able to spring for a $10,000+ preamp
I'd spend the next big chunk on speakers first and a loricraft record cleaner for my vinyl end

But I did audition the LS 25 MK II, and the Ref I and found them lacking to the LS 5 MK II which I still think is the best bargain in the Arc line as far as musicality goes

The Ls 2 MK ii may have been Stereophile top rating at one time but it never blended well in my system. I tube rolled Mullards, Telefunken, Amperex and couldn't tame it. I tried various interconnects to my Arc D200 (solid state) In another sytem it may have worked, and it was the weak link in my system, but once I bought the LS5 it was a herculinian leap and with selling my LS2 for a good price at the time I only shelled out a thousand more