My decision as it now stands: I'm stayin' the course. I still feel I need to commit to more rigorous improvements in my art, and I need to do it soon.
Since there have been a few recommendations along the technical I've received from strangers, I want to make something clear: the SGI is my last computer. I intend to use it until I no longer can upgrade/repair it, something to be treated as a perfect brush.
Part of the reason is that this is what I know. The larger part is that I simply don't want to be stuck using and maintaining mediocrity for the the rest of my professional life. Learning a new OS is, from my perspective, a waste of time. The old hardware and software still works, and works as if it were new, and I have never had an occasion to throw away a perfectly usable brush.
(Then again, no brush has ever frustrated me like a computer manages...)
So. I'm back.