If you are only going to ride at normal speeds most of the time why bother with the big bore kit? You may be able to increase your power enough above stock with less drastic modifications, such as a tuned pipe etc.
On the other hand, if you want it get it. But you must realize that once you have the extra power you will use it. As often as you possibly can, you will not be able to resist the temptation. I know that I would not be able to.