I have a Apexi PowerFC for sale which came with my car from japan. Works perfectly and comes together with this adapter loom but no Commander. You can get this quite cheap used or new from the normal sources.
The PowerFC is a good a option for the people that have good tuner (like Whiftbitz and so on) and want the extra control that a piggyback wont give you.
It will also remove any speed, boost or rev limiter cuts and you can run any combination of injectors, turbos and so on.
Tuning can be done by the optional hand commander or 3rd party products like FC Tune, FC Dataloggit and other programms that pop up lately.
As Ive seen the used PowerFCs go for 500-600pounds with the commander I would like 400pounds incl. insured delivery for mine.