Alright, one last post to this thread.
Before replacing the speaker, I finally found a place locally than had an older (but brand new) HX112 in stock, and I got to try it out, as well as checking out some other cabs, to decide whether I wanted to continue with the hartke sound, or move towards something else.
What I can say is that the HX112 does sound really good, and 2 together is pretty impressive (and almost magically significantly more than than the sum of their parts). It is a very good cab for its price range.
However, there was also a used Bergantino HD112 in mint condition for a mere $400 CAD (that's about $300USD for you Americans!). It absolutely blew away the hartke for me, in terms of volume (efficiency), punchiness, low end handling, and a seamlessness between the woofer and tweeter. Being a cab that, brand new, costs more than double the price of the Hartke, it wasn't really a fair comparison, except for the fact that the Bergantino was priced so cheaply used.
So at the end of the day, I decided that was too good a deal and went and spent an extra $160 to come away with a significantly (to me) better cab.
The downside of all of this is that I may now have boxed myself into spending A LOT more down the road to pair this cab with a second cab, but at least right now, I'm not doing super loud gigs these days, so a single 112 cab is fine for 95% of the gigs I do. Plus the bigger gigs tend to have backline provided anyway.
I may eventually still get the replacement speaker from hartke, and likely just sell the cab for the cost of the new speaker (since that seems to be the going rate for them on the used market), just to declutter my house, but for now I'm excited to have a NCD!