MGIV doesn't do the "semi-brown/eggplant/greyish/etc." But I've never TRIED to get that out of either it or MCC 110, just cool it down a bit and increase D-max. Usually the more profound color change you're talking about takes stronger toner dilutions than I use too, at least with other than warmtone papers. And MGIV is fairly resistant, just not as much so as MCC 110 in my experience. I actually have a couple of comparison prints but scanning just won't show the subtly and it doesn't prove anything anyway since you can make a scan whatever tone you want.
Zsas is right. If the last APX 100 was made in '05, how far out will the expiration dates be, assuming it's been deep frozen since?