"Bests" is in terms of qualities usually sought after by audiophiles, in this case (in most cases actually) mostly detail. Extracting more detail from the venerable Denon DL-103 is achieved at a cost which is acceptable, or inaudible, or unimportant to some; and important and unacceptable to others. The plain vanilla DL-103 is considered by many Denon aficionados (not all, or even the majority) to be the best-balanced and most integrated of all Denon DL-103s: all frequencies singing as a united whole, timing across the frequency spectrum also united and thus extremely compelling, the area which makes the Denon such a classic (also the dynamics and drive, and the large and beautiful midrange). According to those who have owned a variety and come back to the plain DL-103, the extra detail of the other versions disturbs this balance and causes some brightness, aggressiveness and coarseness problems, as well as some unevenness. Others swear by the improvements, at least some of these because they automatically equate more detail with superiority, and deny costs, or do not hear them, or are not sensitive to any cost. I personally love the plain vanilla edition, which I find so good in every respect, indeed supremely balanced and musical to a degree I have never yet heard from any other MC, that I am not remotely interested in purchasing the other and pricier variants. In fact, I would be afraid to mess with the formula, afraid to disturb its supreme balance, which is clearly audible. Not that I wouldn't be interested in hearing one of these variants given an opportunity (especially the "D" version), and see if the balance truly is disturbed. So you've not been misinformed exactly, but it is more difficult to find the writings of those who are willing to sacrifice detail for balance and poise in this era of Detail Uber Alles (a consequence of the Information Age), or even consider these things important.
Viridian, the Denon works superbly well in the Rega RB300, with or without tweaks. I track mine at roughly 2.2 grams, but friends of mine like it at 2.5. I'm still experimenting.