The more explosive strength you have in relation to your bodyweight, the quicker and more agile you tend to be. Some of those lean, 170lb ripped-to-the-bone powerlifters are like quicksilver... they may not look strong or fast, but believe me, those guys are the closest thing there is to men of steel (maybe a misleading comparison since steel = heavy, rigid... ah well, that's the best I could come up with).
Anyways, if you want speed and strength, try to focus on basic, heavy movements- primarily (squat, bench, deadlift etc), and get your bodyfat down.