Okay, here's my suggestions; just my opinion:
Forget Nady, forget Azden
Lowest priced one to look at is:
Audio Technica (~$450):
http://www.bhphotovideo.com/bnh/cont...goryNavigation
Probably one you can't go wrong with, and which just about everyone agrees on:
Sennheiser G2 (~$500):
http://www.bhphotovideo.com/bnh/cont...goryNavigation
I've purchased some VHF ones off eBay before. look for Lectrosonics M175 version. They can be had for little money these days. I picked up two systems for $150 each. Here's an auction with just the mic and transmitter:
http://cgi.ebay.com/Lectrosonics-M17...QQcmdZViewItem
Many frown upon those now as they are VHF; which of course is NOT inherently worse than UHF at all. Originally it was claimed that the VHF bandwidth was overcrowded; I wonder now though, with more and more UHF channels being used, if that soon won't equal out.
In any event, you should NOT have just ONE unit with you that is ONLY one frequency, as that would be asking for trouble.
Best to look for true diversity, multi frequency unit. I like the AT unit above, some prefer the G2 though.