I went from a Shure V15Vmr to a Benz Micro Glider on my LP12/Lingo/RB300. I liked the Glider's improved top end but I missed the bass. Next was a Cardas Heart Reference, which is a better Benz, built to Cardas specs. Bass was back!
Now I have a Koetsu Rosewood Signature and I really have to upgrade my tone arm. Well, it will be worth it.
The Dynavector 10x5 and 17D2 are also very nice-sounding cartridges in their respective classes.
Of course a phono stage now has to be figured into the equation. Since you're into Naim, you're in luck. The Stageline has had very good things said about its sound (in the late lamented Listener, I recall) and it doesn't cost a whole lot to try. The guys at Listener found a hummy one, though, so you might watch out for that.