I have a Grado Blue I've played with the loading on. Grado used to recommend around 10k-12k ohm for all of them, but changed it to 47k ohm recently. Many think this was to end the confusion caused by the odd recommendation they had had, as the cartridge itself hadn't changed any. Grado doesn't use damping on their carts and tend to rely on damping electrically. Joe Grado often mentioned not liking any damping built in.I didn't try going higher on mine, but did take it down to around 15k ohm. It made a slight reduction in highs (and I mean slight) but did sound a bit cleaner (as in less edgy). Again, the difference was slight. I left it at 15k ohm, as minimizing as much listener fatigue as possible throughout the system is a high priority for me, as I have the stereo on all day typically.
Dave