Ok, here's the deal as simply as I can explain it... The X race and X street are so close you won't feel any difference. On a dyno the X race might get you 10 HP more but that's nothing you'll feel. The X street is obviously going to be more streetable than the race due to the fact that the race locks the converter in 2nd through O.D. The race takes a bit of getting used to on the street, or specifically the highway, but it's doable and a lot of people like it (including myself). On either Extreme file you're looking at 400-425'ish RWHP depending on your truck, the dyno, and whether it's a full moon or not. The main difference is the transmission shift strategy.
X race: about 160 HP on my truck
X street: about 150 HP on my truck
street: about 100-120 HP guestimate.