Think of it this way. With water cooling, you've got less fan noise, but they you have the noise the pump produces. Also, the noise is more focused towards the outside of the case, as the radiator needs to sit right near the outside of the case. With a good air cooler, you'll have some louder fan noise (depending on the fans of course), but no other noise. The fan noise is also centered inside the case, allowing the sound to be dampened.
Also, you don't have the chance of bumping the case and causing major damage...
Check out the 690 II Advanced case. I'm using that and the Hyper 212+ on my P2 x4 B50 @ 3.4 Ghz and things are very cool. The 212+ is pretty cheap...I'd say give it a shot before water cooling. The case is setup for water cooling, if you want to go that route.
I actually decided to just go with the normal armor+ and get a cpu fan and heat sink, not because of noise but because im still novice at building rigs and i dont have the confidence yet to install a LCS, nor the cash to buy replacement parts.
It depends on which video cards you have. Up to the 5870 should be alright. That said, I don't think there'll be a whole lot of room left for a LCS. I would want to get a full tower for that, but I guess it depends on what system you were looking at.