I'm assuming you mean squats?
Deadlifts and squats recruit the most muscle, therefore inspiring more growth overall. I think doing all of the major compound movements complement one another, so just adding deadlifts probably wont do a whole lot as far as your bench, but doing deads, squats, rows, benches, pullups, and military presses will help you see overall growth. One isn't necessarily the missing link.
As far as not wanting big legs, trust me, its not gonna be like your gonna wake up one morning and say "fuck, i knew i shouldnt of squatted that much, now my legs are enourmous" it doesnt work that way. Personally I think that heavy squats and front squats are the most important workout you can do for overall growth (again, its not the magic workout, just the most bang for your buck). Try to figure out a way to get a rack, or build something... I use my adjustable bench to do them, it works fine, just make sure you have a spotter. I think that deadlifts are a very close second to squats, but doing them both is where you will start to see the difference in your other workouts.
I'm sure someone else can add more detail, or completely disagree with my statements, but thats just my take