I have a walnut body 5 string bolt (kit) with the Musicman and single coil, active/passive, coil split setup. Lots of variety of tones. I will sometimes put it in passive mode using my Aguilar 924 outboard pre-amp instead of the built-in Carvin pre-amp just to compare . The tones are a bit different- the Aguilar being more smooth sounding off the bat. I can boost the bass knob on the Carvin and get similar results if I want. IMO the Carvin electronics seem to cut through more than the Aguilar, the Aguilar having a more smooth, fluffy sound- similar to my Fender Deluxe 5 string Jazz. On my bass, I actually prefer the sound of the Carvin electronics. I occasionally have to readjust my Carvin neck- no more-so than my Musicman Sterling- maybe once a year. The neck on my Carvin is quite comfortable for my hands and it just feels right when I play on it-no discomfort or adjusting of any kind. I also like the passive/active option which not only gives more variety to the available tones but the security of playing if the battery should go out.
I have played some Carvins (also at the store in San Diego) and also a 6 stringer at a Guitar Center which seem to lack any real bass feel- too upper mid rangy- so I kind of know what some people are saying, but mine doesn't have that type of tone. I haven't tried the newer 18 volt basses-either soapbar or MM/Single coil so can't comment on those.