This isn't specifically answering your question but maybe it can help a bit with your decision:
I love Sandberg basses in every way EXCEPT the sound. That may sound harsh but please let me explain:
The craftsmanship and materials are superb. They're some of the best production models I've ever played. You would have to pay Custom Shop prices to get a Fender of this quality IMO. The fretwork is excellent (and plek'd). The hardware is top quality and I love how they feel. If you like a slim neck (closer to Ibanez SR than Fender) you will LOVE Sandberg necks!
But they are also too bright sounding for me. At least with the stock pickups/electronics. Which is why I custom ordered a VS4 with passive only and a Kloppman PB63 pickup. But even then they used pot/cap values that made the bass too bright for me. It was an easy fix to replace the pots+ tone cap with Fender vintage specs but even then it has a slightly brighter/faster feel than a Fender P (but I guess that may be partly down to my choice of an ebony fretboard). It's a great bass and I absolutely love it but even as a passive only with a vintage '63 style pickup and vintage spec electronics it doesn't quite sound (or feel) like a vintage P. Which isn't necessarily a bad thing of course, just be aware that your not getting a straight P-bass (or in your case a J-bass) clone here.
The Sandbergs I've played never worked for me in active mode. I was never able to dial out the extremely bright highs without ruining the tone. With a passive tone control you can at least dial out the highs.
Lots of people love active Sandbergs though so it all comes down to personal taste. If you want that kind of bright tone you should consider active/passive. If you prefer a more classic/vintage tone, closer to a Fender, you won't really need active. But with the stock pickups and passive electronics it will still be brighter than a Fender, especially with the stock pickups. I guess you could call it a more "modern" tone but to me that kind of bright tone feels somewhat outdated. Vintage is the new "modern" for me I guess but this will of course depend a lot on what kind of music/genre you're playing.
In short: If it's possible, try before you buy and don't expect to get anything close to a Fender J. The build quality is much better than a Fender in the same price range (at least in my experience) but the sound/feel is also very different.