if you are going n/a then i/h/e are the quickest and easiest ways to get your car in better shape. they really won't give you a lot of power like stated earlier, but they will pave the way for other mods to your engine, like cams, or a bottom end rebuild.
the shifting thing is up to you. if you feel better about shifting early, then do it. cars perform differently depending on a variety of conditions. if you feel more power at your mid to high band, then use those to go fast.
mine doesn't loose power until 8200, but i have the cams and computer to thank for that.