Aguilar pre's sound great on fretless basses. Big bottom and detailed upper mids. You can hear one in my lull review in my signature. Always get a passive/active setup IMHO.
The Audere is a GREAT preamp for fretted or fretless jazzes. It even comes in a form factor that installs really easily and quickly. The z-mode switch makes it far more flexible than the stock electronics...