Things to remember when buying wireless:
1) You get what you pay for. The mroe money you spend, the longer the range you have and the better the sound quality.
2) True Diversity is good. Quad diversity is better. 113 recievers is best.
3) You location will ALWAYS affect your wireless signal. Sometimes just not as much.
With that in mind, I can give you a few recommendations. Sennheiser is a great series of wireless. Their EW100 series of WS are well built, have a good long range, and are multiple frequencies. These usually run about $450. If someone tries to sell it for more, they are ripping you off.
Audio Technica also makes a great sustem, the AT3100. Same kind of construction, but with the added feature of frequncy agility, which means that it changes channels for you if it experiances some sort of inteference. These systems usually run around $500.
Shure does have some good systems, but you have to spend out your butt in order to get them. The SLX and ULX systems start at $600, and the body packs are STILL made of plastic.
IMHO, Sennheiser is the way to go. I have a EW172, and it's a great little system. The only time I had problem with it was when I ended up playing at a club that sat under a Digital Cable transmission line. But then again, NOBODY had reception that night, including anyone with a cell phone.
Rock on
Eric