Great decision!!!
You could replace:
As your bass has four knobs, @Al1885 might know a way to utilize that (BTS? BQC?).
As is you can use that config only with VVT…
Me, too, big time. And I own both brands.
My shorty StingRay is well built, but the build and materials on my Sires are waaay off the chart in comparison.
The number you have … plus one. 
I wouldn’t touch this though. this looks great unless there’s something wrong with the electronics. This is gorgeous!
I also think it’s gorgeous and it has some great (German) reviews.
My experience with Harley Benton electronics is soso though. Same for the tuners … though they were on par with the Sire U5 in my case…
If @weedhopper is happy - even better (and cheaper)!
If someone twist my arms I’d put a set of Graphtech Ratio Tuners, White Delano Pickups and OBP 3 on it. I want to keep the large magnet pole piece look.
Oh and a Babicz bridge.
Send it back 
No question that of these two specific basses (the Sterling Joe Dart and the Sire Z7), as I was comparing them side by side that the Sire is the superior bass. Higher end woods and electronics. Fit and finish is pretty good.
I still say the Sterling was made better.
I can find no flaw with how it was put together. It’s solid. Tone knob maybe a little cheap, but otherwise all good. Feels right in your hand.
Sire has some great finishing that they do (rolled edges, etc) but in this case I had to fix the knobs on their behalf as you couldn’t adjust just one of the two stacked pots without adjusting the other, or using two hands. My experience with Sire has been good (I currently own 3 Sires) but they are not without QC issues.
I hear you. Concentric knobs turning together straight out of the box is not unique to any brand. Luckily, it’s a quick and easy tweak.
I just tested mine on my V8. They turn smoothly and independently. I dunno.
The Joe Dart is a well made bass, at least mine is.
Good for you! I am planning the same.
Please post a picture of it.
Great analogy!