Dont expect a seat of the pants gain with just plugs. My advice, go with a step or two colder than stock copper plugs from a good company like motorcraft or NGK, gap them at .054, use some spark plug anti-seize, be sure not to over-tighten and call it a day.
your stock spark plugs are fine...the only thing you will gain is better quality plugs. You will gain 0 yes 0 hp/tq. Personally i think they are a waste of money unless you have some serious engine work done like cams or s/c