Do a search - look at the sticky above and you can also look at other Miata forums (m.net, etc). There is tons of info and I suggest you chat with Ocean over at Chinkara Motorsports (www.chinkaramotorsports.com) since it sounds like you have the Maruha/Freedom IRTB setup. I highly suggest you have someone tune your car who is used to tuning a Freedom unit on an IRTB setup.
Call or Email Jimmy at Fuji Racing (http://www.fuji-racing.com). He has basic kits with a piggy back controler or with the AEM stand alone for the cheaper than the price you stated for the other kit. He's in florida and the kits are made in Japan. I just ordered a set for my 1.6 with the piggyback as I'm going to use Megasquirt.