chakster,
More than a year ago I got a collection of cartridges from a friend who had a home dealership. Due to his age he'd given up vinyl. That included both Grado 8MX and XTZ models. I've had a couple of other Grados but am not familiar with either of those.
I've not auditioned them yet due to rebuilding a 'table. If the XTZ is as good as you suggest I'm sure I'll be pleased. Were they all Signatures? All this one shows on the stylus fitting and cylindrical container is XTZ.