I have owned a TRB6, a BB5000 (passive, narrow neck), BB1200s fretless and a BB5000A (my current fretless). My observations are that the TRB6 was an excellent all round bass if you could handle the width of the neck. The preamp was cool, I could get everything from a jazz bass on steroids tone to a decent approximation of a Stingray or a Ric. The BB5000 was purchased off ebay for $400.00 and I loved the tone so much it became my main gigging bass for over two years. I modded it to have a pan pot instead of a pickup selector switch. My only issue with it was that the bridge pickup soloed was a bit noisy, being a single coil. It sounded good enough for me not to care most of the time. The 1200s was a passive model with a nice ebony fingerboard and it sounded and played very nice. I had a bit of a problem getting the intonation set on the bridge. I eventually sold it to get another bass. My current fretless is a BB5000A. I bought it stock off ebay for $500.00 and I had it defretted and had the pickups changed to Bartolini PJ. This bass sounded good stock but was a bit too rock and roll for my tastes. The tone was nothing like my old BB5000. The P pickup overwhelmed the bridge pickup and I felt that it sounded like an active 5 string P bass (that is certainly not a bad thing, just not what I was looking for). Now the tone is very much like my old BB5000 except no noise and the neck, even though it is quite a but wider is very comfortable to play on.