It is true caffeine constricts your blood vessels causing your blood pressure to rise, as far as it hindering protein and creatine from reaching your muscles, i would not worry about it. There are many advantages to using a caffeine supp before working out and they outway the negs. Ive read about studies where caffeine has been shown to increase calcium in your muscles which in return give you more power...is it gonna be like hulk strength, no not at all but you will have an edge and dosed properly it will give you focus and drive.
I believe your referring to NO Xplode when you mentioned NO x, NO Xplode to me just seems like a sloppily thrown together pre workout, lots of fillers you dont need, i get no focus from it, actually very jittery and horrible workouts. Pre workouts are very user specific but i would give jack3d a try, much more balanced i think and im not hyperventilating putting plates on the bar...just my .02
