The "reasonable level" you should prepare for will be different than the one I should prepare for. Only you know what your nieghborhood is like, where you go, whether you may be targeted because of who you are, what you have or what you are doing. Only you know your level of training and your comfort level with different tools.
I've known people who carry more weapons than internet 'mall ninjas' claim to and who would still be lucky to escape with thier life if attacked by a declawed kitten when they were fully prepared. I've known others that could (and likely would) hand an armed attacker thier own heart when armed with nothing more sinister than a pencile. What is reasonable armament for one is either gross overkill or practicly suicide for the other.
Personally, most of the time I hear someone say that a particular weapon is "better than a sharp stick" I think what they are really trying to say is that the weapon is not something they could recomend, but that if you have nothing better at hand would be better than resorting to hand to hand combat.
Lets assume the average person, reasonably skilled with a handgun, used to using knives to cut things like steak and boxes, and with all the hand to hand combat training that comes from a few fistfights in high school and without any physical impairments. Also assume they live in resonably safe urban / suburban / not to rural area, where police response to a 'shots fired' compaint is likely to be less than 15 minutes and there are no large (greater than 200 lb) carnivorous wild animals. Lastly assume they are not a 'high profile' target (i.e. no known stalkers, don't carry excessive amounts of cash for the area, no reason for people to hate them).
Given those assumptions, a single 5 shot revolver or auto with a reload available or a 6 shot revolver or auto without one is probably a reasonable minimum. Caliber of at least .380 ACP / .38 Special +P or equivalent in energy or momentum. Less than that is probably a little on the light side, but better to have something on the light side than nothing at all. At the other end of the spectrum, a full size auto with standard capacity magazine or a full size revolver, either with no more than a single reload, is probably a resonable maximum. Maximum "reasonable" caliber is anything over the minimum up to 700 ft lbs of energy. A pocketknife, 3" - 4" blade length can be usefull - but more for everyday chores than defense. More doesn't hurt, but probably isn't needed either.