As far as a range for reps, I wouldn't go below 4 or over 15, but I rarely set out to do as little as 4 reps. The majority of my sets are scheduled to work out between 6-10 reps, but like I said it's not set in stone. If i feel like I can do a couple extra reps I won't hesitate to. I always go to failure on every set. The majority of the 12 rep and up sets are my warm up sets. (these shouldn't be heavy at all, just enough to give you a good stretch and warm up the bodypart(s)) The rest of the high rep sets are either for legs or any other body part for a good pump at the end of the workout.
For chest I'd recommend doing db/bb flat press, db/bb incline press, machine presses, DIPS instead of declines, and push ups...
I don't really like flies that much. Some cats say they work great for them, but I think it stresses my shoulders way too much without putting enough stress on my chest. Oh yeah, cable movements can be useful too, but for chest I'd stay away from them until you get the development your looking for using the aforementioned exercises.
As long as you're improving either by adding weight to an exercise or adding a couple of reps with the same weight you used the workout before you're cool. Don't worry about adding weight to each and every set, for every workout, every week.
Smitty's right about the soreness. Initally you'll get really sore. It's just because your body's never been under that kinda stress. It'll come back after you take a break and/or change up the exercises.