Recommend a protein supplement?

Hey can anyone give me advice on gaining strength without size. I know with any gains growth will be invitable but I wanna start doing some climbing and a good strength to weight ratio is essential. Should I do heavy weights with low reps?

Size gains are more to do with diet than training if you want to maintain a good power to weight ratio then you need to be sensible on your calorie intake and type of foods you consumer, also the types of protein....this is going to be a long post, i'll get back to this after dinner!