I can't comment on the Shelter (have not heard it) but both the heavyweight and the VTA adjustment made noticable improvements in my P-25. I am very happy with my Dynavector 17 D-II, Karat. It is low output (0.23mv) and loaded at 100 ohms, it is the best I have heard on my Rega.
Cartridge Match for Krell KPE Reference/Rega P25
I'm having a hell of a time picking a cartridge for my Rega P25 mated with a KPE Reference. The maximum load setting is 1k and so far the two cartridges I've auditioned seem to overload the system: Grado Sonata Low Output MM had the woofers jumping at ridiculously quiet levels. A Blue Point Hi Output MC was better but still difficult to find a compromise that produced quality sound. I've determined that a low output MC is probably what will get the job done and was wondering if anybody had a recommendation. I'd like to stay under a grand. Benz Micro Glider L2 was on my short list. Any other suggestions?