I bought a Zon Sonus just before Christmas. It really is an amazing bass

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The original preamp fitted to the bass was a Bartolini NTMB-918F. The previous owner had this changed to a Keen 3 band with bass/treble cut or boost, mid cut or boost and a selector switch to select the mid frequency, volume and pickup blend.
I'd like to change this, I'm thinking either a Polyfusion, (if I can buy these to have fitted by my guitar tech), or possibly an Audere.
I have an Audere fitted to my Sei bass that's really nice sounding.
Anyone have any experience of both preamps, how do they compare ?
Thanks !