if your budget allows, look for mrmisse at here,
http://www.mrmisse.com/gasmog.htm
he is the dealer for moog stuff locally and able to bring in the moog theremin for you. The moog theremin is the real deal and more features and some of those small building kit sorta which doesnt really sound like the real thing imho
I have tried the moog one and have a discontinued soapbox theremin from LAL(japanese brand). The soapbox one sounded like a toy wheras the moog one, is more sturdy and sounded closer to the old school style theremin.