I'm glad you are happy with the new speaker, but I am wondering how the stock one would have fared with the impedance matched.
I've read a lot of posts about this so I can only repeat it; I'm no expert.
It's preferred to NOT have a mismatch, and not use mismatching to chase tone.
The way I have come to understand it is with a SOLID STATE output section, a higher impedance may be ok but a lower impedance will pull a lot more current, overheat and damage things.
A TUBE output section, when pushed hard, a higher impedance can over work the output transformer, cause flyback voltages that can damage the OT. Output transformers are expensive.
Low impedance will pull more current and work the power tubes harder, shortening the lifespan. I dont recall the extra current draw being enough to put the PT in peril, but I suppose it could.
Also, the extra heat produced may cause mischief as well.