I also have a Mono GM, which has a spherical stylus profile. I've hardly used it, though, because I like the Royal GM II so much--even on mono records. The Replicant stylus digs out much more detail, and my phono stage has a mono switch that sums the channels, so it's a worthy trade off for mono records.
In general, I think you'd find that the more sophisticated stylus profiles will deliver more detail while retaining much of the SPU magic. And, IMO, SPUs need the extra detail because of their bias towards midrange warmth. I'd be far less satisfied with less detail in mine. But if you're really after a vintage sound, spherical might do the trick. I haven't done a comparison with stereo SPUs.
BTW, mine is installed on an idler, too, a Nantais Reference Lenco. In fact, when I was debating whether to add the capacity for a second arm, Jean declared that the main reason to have a second arm would be "to experience the glories of SPUs." I'm very glad I took his advice. Idlers and SPUs are a sweet match!
In general, I think you'd find that the more sophisticated stylus profiles will deliver more detail while retaining much of the SPU magic. And, IMO, SPUs need the extra detail because of their bias towards midrange warmth. I'd be far less satisfied with less detail in mine. But if you're really after a vintage sound, spherical might do the trick. I haven't done a comparison with stereo SPUs.
BTW, mine is installed on an idler, too, a Nantais Reference Lenco. In fact, when I was debating whether to add the capacity for a second arm, Jean declared that the main reason to have a second arm would be "to experience the glories of SPUs." I'm very glad I took his advice. Idlers and SPUs are a sweet match!