So im going to buy my first conealed pistol. Mostly to carry in my truck, and on ocasion to pack around in public. I've narrowed my choices down to three but would like some input from all of you. The choices are 9mm,.40, or .45. I want something with not alot of "kick" and plenty of knowdown. Let me know your thoughts on each of these calibers, thanks!

this will depend on what you find comfortable concealing in the first place. If you are tall and thin how will you conceal a full size .45. it's not comfortable and you will print.

I purchased a .380 and use corbon defense loads. I know, not the most powerful but better than nothing and its not to bad to carry. Bersa Thunder .380

Pretty tough to beat a 40 S&W better punch than a 9mm, easier to handle than a 45.

I agree here.

Decide on a platform first then think chambering. See which models FIT you best and which will be more suited to YOUR individual requirements then think chambering.

there is a reason alot of police agencies switched from .45 to the .40.... alot easier to handle and it's like a 9mm on steroids

I'm leaning towards the 9mm, whats the difference between the 9 and the .40? How much recoil difference is there?

Usually not much recoil difference. It really depends on what weapon you decide to go with. My wife has a Smith & Wesson 9mm that kicks more than my XD 45acp. You really need to find a weapon that fits you.
The big difference will be in the knockdown power, in that department the .40beats the 9mmeverytime.

I have a 9mm Springfield XD I love it but if I had to do it over I would have went with a 40

Well, sounds to me like what you want doesn't exist, since it would have to defy Newton's Third Law of Motion (for every action, there is an equal and opposite reaction) to have plenty of knockdown and little kick! No gun can hit harder than it recoils, since these two actions are equal and opposite.

IF you want knockdown in a handgun, you will have to master the recoil of a round like the .45 ACP. Kimbner makes some really nice little, easily concealed .45's!IMO, in a semi-auto this is about the best you can do.

However, the 9mm and .40 S&W will work pretty well, IF you learn to shoot them well enough to put the bullet somewhere that results in a fast stop of the fight! Both of these cartridges lend themselves much better to makinga small hideable pistol.