I have, but not in a Zon. Definitely more open sounding than the Bart, but if it'd be enough is a tough question, and it's a $300 preamp. If it was me, I think I'd try it though, with a bass that nice... I'd really want to exhaust all options before deciding to flip and continue searching for "the one". I can tell you this, tho, if you do flip and move on, definitely get something with a harder top like Maple or Koa or similar. That should do it. Then of course, at least IMHO, the J style pickups are more open sounding too, so maybe consider moving back to the regular Sonus 5.
Just some thoughts anyway.