Cost/Performance ratio is always in favor of air cooling.
h80i is about as good as a mid-high air cooler, and twice the cost. Great for ITX builds though.
h100i is considered an excellent cooler, but for $60-80 you can buy an air cooler that performs just as well. (There are of course equivalents from antec etc for closed loop coolers, but they all pretty much use the same manufacturer/design)
Open loop is the most expensive, and most effective. But requires maintenance and you have a greater risk of leaks.
well i was looking at getting another 670gtx and watercooling them to give them a longer life than if they were air cooled, and if i was going to do that the cpu seemed the best option to make it worth while,
Look then u have to get a custom water cooler set up that would be combersome plus risky there are many companies sellin parts for it like xspc,koolance,swiftech,bitspower etc it ll cost u much more but excellent results
Just make a check on all tubings and fitting sixe
You'v already got yourself a high end air heatsink, getting a CLC option wont really net you much extra performance over what you have.
I suggest you go into a custom water, especially as your considering putting GPU's under water. Its expensive, but your going to get the best possible cooling results until your chilling the water.
I dont think installing it will be a problem just finding the correct parts to install it,
would i see a decrease from the Jetstream air cooler already on the card? I think the GPU is the part im most concerned about, the pcu doesnt go over 75 on prime 95 as it is,