I'll tell you what I would like to hear, a SP-10 Mk 3, that is maximizing that circuit with the best parts and see what we end up with. I know, I know the design is a bit long in the tooth compared to today's but I wonder how much better it could be. And of course there is that great phono stage. Great Northern had several mods for this pre and stated the extreme mod would compete with anything out there, and what about the LS5? How much more could be extracted from that great line stage with current parts and a few changes? And so far as going backward who here would say that the Classic series amps were an improvement over the D series amps? Not me for sure! Now the VT series got them back on track.
I haven't heard current production other than in unfamiliar systems so I won't comment but it seems unlikely that their middle of the road line stages couldn't be more than minor changes in circuit design. There is a benefit for ARC in promoting new models rather than making revisions to existing which is to say some will want the latest and greatest, not a bash on ARC but I don't particularly care for this approach, preying on the known insecurities of audiophiles:)