want more power for as little as possible

I had just bought a 2007 ninja zx-6r. Love the bike and ride every chance I get.  The problem is that I want to get every last horse out of the thing that I can. The thing is that I am married with 3 kids and do not have alot of extra money to be blowing on parts  , so I am trying to do the best mods that I can for as little as possible.  Any suggestions, please help.  

If you put a data-logger on the thing, odds on you would find that you have only used the full 120 bhp for about 2 seconds in every hour of street riding you do, even when you think you are really 'on it'. So if you did get an extra 5bhp peak out of it, at whatever cost, you'd never actually notice. But if getting those extra bhp at the top end screws the mid-range or the low-end tractability, you'll actually 'improve your bike worse' for the riding you actually do the rest of the time.

The other thing is that as a rule, the best upgrade you can do to any bike is to the nut behind the handlebars.

There is no bolt-on performance goodie that will make you faster and safer at the same time, or indeed give you anything like as much performance bang for the buck as additional skills training. For you that could be MSF ERC, or a track school like CSS.  

I agree with khaylock, but another thing you might want to look at is sprockets. It will either take away from your top end or your bottom end. If you get a sprocket set up to help you on your take off you will notice it in all that you do. But your top end will get slower. But as khaylock sais you, more than likely, never use all of what your bike has. But try the sprockets it will help you alot. Becarefull and ride safely.