I am replying in answer to my own question in the hopes that it will assist others who search for an answer in the future (Thanks, Jakob, for your informative reply!).
I received the HA-1 unit yesterday and it is indeed a worthy upgrade from my Vox AmPlug, that has been my companion these past four months with my wife working from home.
The AmPlug is a great tool, but in a completely different league from the PJB BigHead. The HA-1 is just like plugging into a "Big Head" or any other high quality amplifyer, which is exactly what I was hoping for.
The AmPlug just doesn’t have the clarity and/or definition I was desiring. It doesn't transmit the ringing of unmuted strings well, or the "clack" of poor fingering techniques, etc. and was allowing me to be lazy with my technique. The BigHead is very clear and with good phones (Sennheiser HD-25s) highlights my mistakes, which is what I am looking for as a new bassist. It's fidelity allows me to hear those things I need to work to improve on and which would come through when played through a quality amp/speaker.
The HA-1 is a beautiful, very well constructed unit. Quality is impressive. I will enjoy the ability to tweak the tone via the two-channel EQ (Bass & Treble, boost & cut).
As far as mobility goes, I’ve hot-glued the BigHead to an old iPhone OtterBox belt clip. Works awesome and truly allows me to be mobile and wander about while playing vs. being tied to an amp plugged into the wall (just like using wireless). Hot-glue just peels off when you are ready to remove it, which I don’t expect to do anytime soon.
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