ARC Ref 1 vs. ARC LS-25 I vs. ARC LS-25 II

I own the LS25 MKI. The MKI with NOS 6922 tubes (6H23), in my opinion, surpasses the LS25 MKII in terms of tonal quality and musicality. Also, The MKI with the NOS equals the MKII in terms of dynamics, midbass solidity and impact. Of course, the results are dependent on system/personal preferences.

I owned a late model REF1 which I replaced with a LS25 MKI several years ago. At that time I was using Quad USA Monitors and a VT100. I thought that the LS25 was very close to the REF1 in my system: to me, the LS25 had an edge in resolution, whereas the REF1 seemed to have a slightly better soundstage. There was not enough difference to justify the price difference and I hated burning 8 NOS tubes in the REF1 verses 4 in the LS25. Good Luck!
BTW, with your VT200, do you know if there is a single bias adjustment for each octet of 6550's?

LS 25 II win easily ! MK II much more detail with super wide soundstage which i loved about that preamp !

My system is as follows
cd player: Meridian 508.24
pre-amp: none(just sold via AG)
amp: Mark Levinson No. 27 for sale via AG, to be replaced with an ARC VT200
speakers: Sonus Faber signums w/REL StrataIII
speaker cable: Nordost SPM
I.C.: Nordost Quattro fil XLR
Others: Transparent Power bank, Cardas Golden power cords, Meridian 504 tuner(for sale)

Have a LS-25 Mk.I that I have been very happy with. Not sure how it stacks up against the Ref I or LS-25 Mk.II as I have not A/B those units in my system. The LS-25 Mk.I did better my previous Sonic Frontiers SFL-2 and Mark Levinson 38S by wide margins. The sound of my LS-25 has been greatly improved with both NOS tubes and full Marigo dot treatment. I also have had good luck with a CPCC Top Gun on the LS-25 Mk I. The LS-25 Mk.I also successfully drives a relatively long interconnect run (25 Feet) to my amp. Hope this helps. Good Luck.