Unless you have a good grasp of processing theory, the Symetrix is not a plug-and-play box. Come to think of it, none of the mic processor boxes are. The AirCorp or Rane units have fewer knobs, so they may be slightly easier to get something that is close to what you want.
But it you sit with it and have the patience and read the manual, the Symetrix will do everything you want it to and sound exactly the way you want. But, ya gotta spend the time.
I have heard things about the Aphex unit.