jb90

They're not as important for bassists as they are for guitarists.  Just get some pickups that can give you everything you want to hear.  Although bear in mind they're passive (therefore subtractive) in their effect which means they can take frequencies away but they can't add them.  Also, they are fairly coarse in how they respond so you can ask for a peak but it's quite wide in it's bandwidth, you can ask for highs to be taken away and added but if you add them then usually there is a sacrifice in warmth.  Conversely if you want warmth then you can get it but it means the pickup becomes woollier sounding - although that can be remedied to a small extent with magnet type (ceramics) and wire (thicker).  But where that leaves the mid peak you asked for after all the faff is anyone's guess.

As for preamp, if you're nit picky then get something which gives you the control you want.  The frequency centres can be quite important for bass, mid and treble. 

But if you are looking for a particular timbre (ie. how can I make this bass sound more like a Smith/Rickenbacker/Status/Alembic), neither will give it to you by themselves.  

@Higgie Great sound! I'm corious how it sounds in fretted StingRay but on your fretless there's a lot good growly mids which I like in bass. It's always give you sound that break through the mix. Thanks. And how you solve problem that the input jack is in different place than in original StingRay bass? 

Check the John East site. He makes different versions depending on if you have a 2 band or 3 band Stingray. The 5 string has the jack on the side anyway so was just a direct drop in replacement for my bass.