The best for that money is pretty much the Sennheiser G2 system. I have the original system, and have purchased an additional newer G2 ones. They are backward compatible, and you may be able to find the original system, for much less, just buy it from a reputable seller. If not you can get the G2 transmitter, receiver and plug on transmitter for your price range, in the US you can try B&H in NYC or Gotham also in NYC.
The newer system has a couple of added features like RF confirmation. They are rarely interfered with I use mine in NYC all the time, which is probably the RF capitol of the world and never have any problems.
They had announced a dual receiver, dont know if it has come out yet, that is definately a great feature..