Yes, the LS5 is the only preamp (line stage) in ARC history other than the PH2 phono stage, that has ONLY balanced inputs and outputs. Both of these models were the first to have truly matched balanced circuits in the ARC line. Models like the LS2B or LS3B had XLR connections but were single ended designs. The LS5 and PH2 came at the end of the end of the Classic and V series amps that then phased into the outstanding balanced-inputs-only amps, VT130 & VT150. Later ARC came out with the LS22 and then LS15, Ref1, models that had all sorts of inputs and outputs. The LS5 MK III followed from the Ref1's design and to many of us who heard these two models, the LS5 III was prefered. It simply had more of the midrange bloom and 3D. But all of the LS5 versions have this quality. I simply do not see the value for the Ref1 in the $4k range on the used market. So much can be gotten now for $4k that brings on so much beyond the Ref1 now.
After 7 years with 3 LS5's, I was ready for a change and the BAT 31SE was a natural progression for me. But the LS5 and PH2 will always be remembered as components in my system that brought years and years of musical enjoyment. These paired with the VT130 amp were an incredible synergy .... wow, awesome midrange bloom and harmonic richness. I then switched to an older pair of ARC Classic 150 amps in hopes of more power for my Magnepan 3.3s, and indeed I got a little more headroom, but much of that special quality of the VT130 was gone.
The PH2 especially is a killer phono stage if you are willing to put up with the balanced connections as well. It is perhaps the most neutral product ever in the ARC line.
I did hear the LS25 and the presentation was quite nice at the ARC dealer, but I never had a chance to do a shootout with this at the dealer or at home vs the LS5 III or BAT 31SE. Just stay clear of the LS2 and the Atmasphere MP3 as these are not in the same league. Lots to learn if you take the time to listen and compare. And if you do not get too attached to any product line, you can often get so much more ... and for less money.