Note I mention "favorite," not "best," which I believe might help generate more useful responses. I have three cartridges: Ortofon 2M Black, Denon 103, and Fidelity Research MC201. Currently I listen to the Denon via a pair of Cinemag 1254s.
I want to try out a better (than my 2M Black) high output (non-MC) cartridge that best mates with the Simplex's arm/damping. I want more euphonic beauty or lushness, I suppose, than what the Black offers. I listen to a lot of classical. Maybe I can do a better job of aligning the Ortofon, but as you know, WTL locks in a lot of crucial adjustment variables. I've tried various VTA settings, and I now just have the arm parallel with the deck. VTF is about 1.7 grams. Golf ball is about 1/3 of the way into the silicone goop.
Because the Denon is low compliance, I experimented with putting more weight on the Simplex's arm by wrapping some solder around it and back behind the counterweight: after weeks of listening, I didn't notice any difference. Removing the wire didn't make much difference either. I suspect the strong damping of the silicone fluid is more influential.
My analog chain is good: LTA MZ2 preamp, First Watt F4 amp, Omega Alnico high output monitors. Phono preamp is one I never see anyone mention, a SofTone Model 4, bought directly from builder Shoichi Yoshimoto in Yokohama. I like it.
http://softone.a.la9.jp/english/index.htm. I have had others, and have built a couple, most recently a RJM Emerald, which was good, but not as good as the SofTone. I have an EAR 834P clone PCB that I will build up "some day."
Used cartridges are fine, if there are replacement styli available. I'm mostly wondering about Grados and SoundSmith options, but I'm certainly not locked into just those brands.