That's definitely something to consider as well, as there's 2x12 cabs fairly commonly available used. I had played and really enjoyed the 4x12 Orange cab before I bought the 1x12, and you can hear a pretty how much different that is compared to the 1x12 here:
The Katana Artist I had before was like an oversized 1x12 open backed cab, and that had a pretty decent low end response although it also had some nasty upper mids. The Fender FR-12 is a bit bigger than the Orange and the low end is massive, although it's a different style.
When I run the Rocker 15 through a load box and into a cab sim it sounds a lot better. It's still not my cup of tea but leads me to thinking it's much more the cab than amp.
Having read through the thread and aware of your gear history through other threads, I'd agree with everyone that it's a speaker situation (cab & monitors). Which you alluded to early on as well.
--V30--
Recently tried a bunch of fender BFs, tweed Bassman and a Traynor 15W at a store.
All low volume.
The Traynor with a 1x12 V30 sounded so bad.
Same frequencies stood out in the video you posted w/ Orange PPC 1x12..
Couldn't dial it out with the guitar/amp controls.
--Cab vs Monitors--
My current setup is studio monitors
Used to have 2 amps, wet/dry. 1x12" and a 1x8".
A few times I tried the 1x8" at conversation levels..
Under 74 dB, even the 8" speaker was muffled and lacked clarity.
At those volumes, monitors for sure.
For 80-85 dB and above, I'd keep a cab around for a better experience, even if occasional.
--High end & EQ cuts--
With monitors, I struggle with the high end as well.
Use multiple EQ cuts, and as low as 5 kHz.
But my issues are only at high-ish volumes, (>85 dB in a small room).
At low volumes, I can manage and have a great experience through monitors.
> If you enjoy the cab experience, even at low volume, perhaps try some cabs or a mellower speaker.
> With monitors, I'd rather just cover the tweeter with something..