Question: How is your noise floor?
Is it acceptable to you, or do you crave a deeper, darker, blacker background?
I ask, because for a couple of years I used the Shelter 90X, (after having used a couple of Koetsu cartridges for a couple years), and while the Shelter had great frequency extension, better than either of the Koetsu cartridges, (especially in the bass response, where it is a real champ!), its noise floor was not as good as the Koetsu cartridges to be honest. (It was not bad mind you, just not great.) And, while I loved most everything about the Shelter, I found that I kept yearning for those deep, dark, black backgrounds that the Koetsu's had.
Eventually I ended up upgrading to the Dynavector XV-1S, (the same cartridge that Raul has already recommended), and I am now completely happy with my analog system. (Or as happy as any audiophile can be anyway.) It has great bass response, (either as good as the Shelter, or very nearly so), the mid-range, while not Koetsu lush, is still very, very nice, and the treble extension is better than the Shelter, as it is much more refined. The tonality is just perfect, IMHO. And, it soundstages and images incredibly well. And to top it off, it has those deep, dark, black backgrounds that I wanted so much! (For me it is the perfect cartridge, and one that I have no plans on ever upgrading from.)
As far as the tone arm is concerned, I went from a Rega RB900 to a Basis Vector M3, and it was a nice step up, (more resolving, better bass response, quieter, etc.). But to be honest, I feel the change from the Shelter 90X to the Dynavector XV-1S had more of an impact on my system's sound that the change in tone arms. (The upper end Rega arms (R600 and up) are pretty good, albeit with some limitations, such as a lack of VTA adjustment, and a slight lack of refinement. But over all, I felt they were a good value).
My two cents worth anyway.