I am not a fan of wireless for guitar or bass, haven't really dealt with a unit that didn't have some sort of signal degradation or frequency loss. If you are going to do it you have to get a good quality unit. Without breaking the bank check out the Samson Concert 77, I hear its not too bad. For a real nice Sennheiser or Shure system you could be spending around $800! (That's not even for a rack mount unit), for something that a $20 part does even better, but not wirelessly. Personally I'd rather buy another guitar.
YMMV.