As it turns out, my speaker is of the 8" category, despite measuring just a little over 6" (like 6 3/8")
I found an inexpensive 8" coaxial ceiling speaker today, with a nice sensitivity. It is a speaker intended for in-ceiling pa systems, and 25/70v, with a transformer.
I took the transformer off, and reverted back to 8ohm. Beyond that it was a straight bolt-in swap out.
Overall, it was a substantial improvement in both high freq, and low end.
The low end of the original had a fuzz around it, and the highs were getting smeared in distortions.
Now with the separate drivers, each is handling its own range without the smudging. The bass is far more refined and articulate. Its now more appropriate as a corner speaker, as there is far less tendency to overstate itself and get fuzzy around the edges.
The highs,... well Sarge has commented numerous times already about how much more revealing the highs are, suggesting sizzle in the cymbals where there was none before.
So we've freed up the high spectrum substantially as well.
Overall, even with an inexpensive speaker, its a fine improvement. Its probably not an ideal speaker, but, a very reasonably priced excursion and experiment. So, I now feel it a reasonable endeavor to upgrade it to an even finer degree. I'll let this run in for a bit, and see where it goes, as its enough of an upgrade as is, to not feel a need to change it out too quickly.