I'll bow to your superior experience - I've only heard one twice but it didn't make me want to own it on either occasion and there wasn't a stack of other turntables available to race it against. Most people will be lucky to hear one at all given how few of them there are out there!
Out of interest what proportion of the total world Rock population do you estimate your collection represents? I've not seen a serial number above 500 on a Rock 2 so it could be a few percent.
You are right, very few have heard a Reference at all, let alone back to back against anything else. Apart from Max, myself and a few other few persons I know, some of whom are no longer with us, sadly. There's probably very few other people that have heard two against each other, or had the chance to compare with other decks. I had both a Voyd 0.5 Reference and an Avid Acutus at the time I had my first Reference and compared that to an SME 30 at the time, which was fabulously built but didn't do much for me, musically, although I remain a fan of SME (of old, at least). The Reference stayed and the rest went, for varying reasons, mostly of space, but I actually preferred the Reference, despite liking the 'differences' between them. Back to present day, I have a top of the range Helius Viridia/Omega Silver Ruby/Transfiguration which sits in my system next to the Reference, Lyra Etna SL, along with one of my top spec custom Rock 2's, with modified ceramic bearing'd, Kondo wired, Excalibur and Koetsu Urushi Sky Blue. The reference is fettled but unmodified, otherwise. I'm happy to demonstrate any to anyone. Numbers wise, there were around 3000 Rock 2's made according to Max. The latest one i've seen is a NOS boxed one with Excaliber and Merlin that I have here which has never been used and is still in its protective bag (which I HAD to open out of sheer curiosity!) - its a late serial number and has some differing features to others I've seen. Thicker platter mat on the platter, different bearing design and motor board style and different feet. The subplatter is very thin where the belt runs, I guess, to account for 1) the fact the belt doesn't have to be moved, because it has a Merlin, and 2) to account for the extra thickness in the platter height due to the increased platter mat thickness. In reality though, there were many changes throughout Rock production (almost by batch!), as Max experimented a lot with bearings/subplatters, feet and motor boards, which may have also coincided with supply, cost and availability. In reality, there was very little that didn't change, even the writing on the trough did. I think maybe the motor and the switch were maybe the only things! Later decks were much nicer in their finish than earlier ones, especially compared to the earlier ones with the smaller diameter shaft and non-adjustable sub-platter height. Really early ones never even had a screw in clamp. In terms of number spread, many stayed in the UK but there were a lot sent to Europe and they were VERY popular in Germany and Holland, and much less so, but some went to parts of Scandinavia. A portion went to the US (which is one of the reasons why the later Rock 3 was manufactured and built there and is pretty rare here) and an amount went to Japan and the far east, so I'm told. The Rock 2 is by far the least rare of all the Rocks. Amounts are vague for the Rock Reference (varying between 49 and over to 150, but I think its more likely somewhere closer to the lesser amount depending on who you ask). I've only ever seen 7 different ones....I know they are revered by Japanese collectors and several have gone to those guys over there from here for over 10k... Rock V (between 38 and 55, so they're very rare - mine came from Switzerland and I know Mik at Unique Audio has one, but thats all I know of). Rock 7, funnily enough, I never actually got round to discussing with Max, with respect to numbers made, although I do know the majority were sent to the US, plus here and Europe. Of course, the rarest of all are the various prototypes, the Rock anniversary and the Rock Reference Master. I have the Cranfield Prototype here, currently, along with Prof. Jack Dinsdales old Rock 3 (and 2 other Rock 3's). The Anniversary I've seen bits of at the factory, and sadly, The Rock Reference Master which I've been looking for, for years, hoping it would come up one day, has never re-surfaced. Max sold it and its never been seen since... not even he knew where it went.
So all in all, Rocks are actually pretty rare. I've had around 80 or 90 (ish) Rock 2's through my hands in varying forms plus doing work on others for people. Very few References come my way, and even fewer V's and 7's. Literally no 7's at all in fact, for work other than set-up/ tuning. I guess they're just not at that point yet where they need work, or have all been squirrelled away and are not in use, due either to people moving over to digital, or just not working and been put away? Either way I think their numbers are similarly limited. It was obsoleted by Max just before the vinyl resurgence...
All the best
Matt