RE: goldtip XT vs CX 300
I personally would recommend you spend a bit more and invest in either the 3D Pros' from Goldtip or the Carbon Express 3D Selects. The extra QC and tighter tolerances are worth the extra dinero.
However between the two shafts you mention (XT's and standard CX) I would recommend the CX. The last dozen XT's I bought went south in a hurry.