Those are pretty good brakes and the stock pads should stop you fine, if well adjusted. I had the same problem when I moved to a road bike, some people suggested I rough up the pads with some sandpaper, since the brand new surface is smooth. I didn't do that, but I just kept riding it and cleaning the pads / rim surface once every other week or so. I guess the natural break-in of the pads from use did the job, and I can stop very quickly. I'm also more used to using drop bar levers now.