Xientist,
If your're rich, just get Xtreme IV.
If u're man in the street, get Xtreme III- Performance is fast enuff, and price so much cheaper, about $75-$80 (dunno if lower now).
Xtreme 4 = BMW 335 ($230,000) 0-100kph in 5.5sec
Xtreme 3 = Civic Type R ($100,000) 0-100kph in 6.6sec...