Cool! Yeah, I love those guys! That store is super helpful! Sounds like they turned you in the right direction! I love thicker J [pickups at times, but they have a built in sound that may not lend itself to what you were looking for, so the one they recommended should to the job.
In my experience with J basses, Bartolinis sound a good amount more modern than some of the more traditional styled pickups out there. That's not to say they can't do "old school", but they just sound a lot smoother, and that's a great thing if you like more of a consistent sound that's maybe not as "raw".
With the players you mentioned, much of their tone is based off of their signal chain, not just the pickup. You did say that you wanted a modern take on it though. I've heard that the Bartolini bi-axis pickup gets a large J-type tone also! One thing I like to do when setting up instruments for myself and others, is really hone in on the pickup height. Some basses really respond differently with different heights, and with a fully covered pickup like the bartolini, you may have more options with them.
