So I went to change the hub on Saturday and found that miraculously, the wheel isn't loose anymore........very odd. I shook it every which way, and spun it and heard no noise or resistance. So I'm going to hold off on that for now, and keep an eye on it.
I did get the 05 Forester XT cat back installed tonight though. I used an MS3 adapter, which aren't made anymore. Worked great except for the typical hassle trying to find the right sized doughnut gaskets at the local parts store, but I found ones that worked. It has a deeper, more rumbly tone to it now, and definitely is louder, but still pretty quiet at normal driving. But it's newer and in better shape, and the sound improved, so I'm happy with it.