Here's some general information that'll help you start your journey.
IMWNP: Audio Ltd. 2040 at about $5K per set. Best distance I've measured. The best sound I've heard.
Lectrosonics: about $2500 to $3k per set.
Zaxcom: about $2500 to $3k per set.
Sennheiser makes a line of wireless from $500 to about $3K.
Sony makes analog wireless but has a digital wireless system due out this year. I forget the projected price, but over $3K. Jury still out.
Audio-Technica makes a line from $500 to about $3k.
MIcron: I don't have a lot of info on Micron.
Depending on your setup, you may benefit from antenna distribution systems and directional antennae.
I use Lectrosonics 411A's w/400 transmitters and love 'em! They sound hard-wired! I like the fact that they are a digital-hybrid (meaning they use an analog carrier to transmit the signal) instead of being all digital. The reason is that with digital, the signal is ether there or it isn't; with analog at least you'll have some kind of siginal. Of course, in a studio, this might not be as much of a problem as in the field :o)
In any case, never cut corners on wireless; remember, your system is only as good as your weakest link.