I have a GWB35 that has been upgraded with a custom Nordstrand Dual Coil Pickup and a Bee Pre. I sold a standard GWB35 to buy this one that was already upgraded so I have used both and the difference is astounding, but I can't tell you if the preamp or the pickup has added more.
[attachment=29626:gwb_bass.jpg]
[attachment=29627:bass_pre.jpg]
A quote of mine from a previous thread:
[quote]I'm not sure if it the Nordstrand Dual Coil pickup or Bee Pre is the main contributor, or just a combination of the both, but the output is much higher than the stock electronics. And the tone is lovely and full, and very very quiet in noise terms. When rolling the bass (or any control for that matter) full on, the tone is every usable. Just having the extra tone control options on the bass is very nice. I always liked having a very simple volume, tone layout, but the additional features the previous owner has added has only enhanced the sounds you can get out of this bass.[/quote]
I have no idea what a Bee Pre costs but the web link is here: [url="http://www.beebasses.com/html/bee_pre.html"]Bee Basses Website[/url]
There are some recordings of the bass at [url="http://www.myspace.com/daniellabove"]Daniella Bove's Myspace[/url] that give you some idea of the sound, but I'm based in Milton Keynes and you are more than welcome to come and try it out sometime.