there’s the ‘sweep-profile-3d’ tool in zbrush, would be useful to get the initial shape for those amp dials. it also gives you the option to create ridged/knurled edges quickly.
knowing what you want to use it for (I’m a happy toneport user!), I suspect zbrush would be more useful for you than a traditional 3d package. others have mentioned zbrush’s roots as an illustration tool, which sits well with the existing gearbox look and feel.
there have been a few people over the years that have pushed the ‘airbrushed mechanics’ look, you might find it interesting to see some images, read how they construct them. a lot of these come from v1.x, well before the lumpy monster head brigade pushed zbrush to where it is now… 
ztevie ray waaay back when did lots of this style:
http://www.zbrushcentral.com/zbc/showthread.php?t=000387
here’s a few posts explaining his techniques:
http://www.zbrushcentral.com/zbc/showthread.php?p=82102#post82102
http://www.zbrushcentral.com/zbc/showthread.php?p=107663#post107663
good post showing how to make tyre treads quickly, it would easily apply to ridged dials:
http://www.zbrushcentral.com/zbc/showthread.php?t=001440
mechanical robot bits, script included (curious if it’ll work in z3!):
http://www.zbrushcentral.com/zbc/showthread.php?t=001965
tricks to fake booleans:
http://www.zbrushcentral.com/zbc/showthread.php?t=009776
using simple alpha images to construct 3d shapes (guitars in this example!) get too close and they don’t look good, but would be fine for a gearbox UI:
http://www.zbrushcentral.com/zbc/showthread.php?t=010952
and another one:
http://www.zbrushcentral.com/zbc/showthread.php?t=21517&page=2&pp=15
this airplane is a good example of something much easier to model in something like silo, but shows you can do more than most people expect in zbrush (there’s a certain macho pride in keeping it all in zbrush too… 
http://www.zbrushcentral.com/zbc/showthread.php?t=020370
more crazy detail revolved surfaces:
http://www.zbrushcentral.com/zbc/showthread.php?t=5574
for rendering rotating dials, I think it might be easier to render all your elements seperately, then composite them in after effects. you won’t get highlights or reflections properly moving over surfaces as they rotate, but i doubt people will notice much. if it really bothered you then use marcus’ script to render out the rotating dials, and import those to AE. While you could definitely do all your finished work in zbrush, it’d be faster to composite externally.
-matt
ps: new products eh? cmon, spill the beans! an updated variax would be nice… hint hint