Doug mentions what is more important in your choice than matching to your preamp - matching to your arm. The Dynavector mentioned may be the best way to go, see if you can audition one.
As far as the Grados go, the hum source (if experienced at all) can generally be rooted out and addressed. Personally, I don't think the Grado "dance" has so much to do with suspension breakdown, at least in the sense that it would be seen as an inherent weakness in build quality. These Grados should be mounted on a lightweight arm and they will sound very nice, indeed. Mount one on a heavier arm and you might be ticketed for a dance card and THAT is what also could lead to the breakdown that Doug mentions. Otherwise, there are folks with Grados on lightweight arms that experience very long life cartridge life.
As far as the Grados go, the hum source (if experienced at all) can generally be rooted out and addressed. Personally, I don't think the Grado "dance" has so much to do with suspension breakdown, at least in the sense that it would be seen as an inherent weakness in build quality. These Grados should be mounted on a lightweight arm and they will sound very nice, indeed. Mount one on a heavier arm and you might be ticketed for a dance card and THAT is what also could lead to the breakdown that Doug mentions. Otherwise, there are folks with Grados on lightweight arms that experience very long life cartridge life.