Ok, I guess the question here is how much power are you looking to get? What are you doing that you need more power? Where do you want more power? Low end, mid-range, top end?
Will a full system make more power? Sure, how much more? Not a whole lot, maybe 2-4 hp more. It is usually the weight savings that a full system brings that helps. Now, I haven't looked at the 10's stock exhaust (as mine is still stock) compared to a full system yet...and really I don't need to. The bike has all the power I need, and then some. When you go to a full, you ditch the converter...so as long as you don't have any type of emissions testing in your area, you will be ok. What you didn't mention having on your bike is a way to control your fuel delivery. Noticeable gains can be had by properly tuning a fuel curve (and no, most people who run dynos can't get every bit of power out of a bike). Another item that would help greatly in your search for every higher hp numbers would be an ignition module or advancer. Kawasaki has always left power on the drawing table by keeping timing on the soft side. More than likely it is to keep emissions in check, but either way, bumping up timing will help power throughout the RPM range. As for your filter question, I don't believe in many aftermarket filters. Being a diesel truck guy, I have stumbled across enough proof that most oiled cotton filters have increased flow numbers, because they do not filter air as well (filtration is sacrificed for flow). I don't know about you, but I will keep a stock filter, even if it is costing me an extra 1-2 hp on the very top of the RPM range. Last but not least...cams. You state that you don't want to hurt reliability. Cams will not normally hurt reliability...but ride-ability usually suffers. Race cams will take away bottom end punch, and some mid range power to give you maximum hp at high revs. Great for a race track...but very bad for the street.