Congratulations on your new gear. I owned a Grado Sig arm for a couple of years, mounted on a VPI. Good arm; should work very well with your Grado cart. BTW, is it XTL or XTZ? Probably XTZ. The XTZ, which I also owned, was Grado's top cart several years ago. It was notable for being the first of the moving iron Grados to depart somewhat from the Grado "house" sound. It was more detailed (a la MC) than the others in the lineup. It's output was also lower than the others; somewhere around 1.5 millivolts, as I recall. It was perhaps a little polite sounding, and a common tweak was to use the stylus assembly from the model below it (the TLZ) with the XTZ body. The TLZ cantilever was not as damped and provided a somewhat more lively sound. If you are going to replace the sytlus on the XTZ, I suspect that it will be difficult to find an XTZ stylus, I have, in fact, seen a couple of TLZ replacement styli for sale over the last couple of years. Not much I can tell you about the arm, other than that if you notice a bit of play in the horizontal bearing plane, it is normal; the arm was designed that way. Don't try to adjust the bearing play yourself, it was almost impossible to get it back to how it was from the factory. Also, I recall that attention was paid, as advertised, to the quality of the arm-to-preamp cable; it was pretty good. I actually at one point replaced the internal wiring of the arm with Vandenhul silver wire and filled the arm tube with foam for a nice improvement in sound.
good luck
good luck