Motec and Autronic are top end ecu's and real expensive that are probably not required unless you want mega hp, eg 600hp.
Microtec, Wolf are cheaper options, however I am looking at getting a Haltech fitted, these are a little more expensive than the other two but have a few more features and will tune a little better. It really depends on who tunes the system as to how good you car runs and there are so many different ecu's avaliable which everyone recommends something different.