I can't claim to be the most awesome kicker in the world and to be honest I haven't kicked for my team for a while and have as a result lost some distance. One of the big things is understanding the intricacies. Rugby, is generally quite a "wide stance" game. However, kicking off a tee is a little different. As you have to get you placing foot (i.e the foot you're no kicking with) as close to the tee as possible and in the direction you are kicking, the stance is certainly narrower. You get your power by transferring the weight you are taking on your placing foot to the kicking foot. This is acheived by a reasonable take back and high follow through. If you have the placing foot in the right spot and you have your head over the ball you shouldn't need to try and kick really HARD. It will be a natural progression, because you're connection will be good.
As a side note, if you have you placing foot directed to where you're kicking, no matter you kicking style you should be accurate. This is basically due to you being square to your kicking direction and as such giving you balance, even with a narrow stance.