OP- Unless you're trying to cut down on noise, and/or are struggling with air cooling to begin with, you shouldn't really need liquid cooling. Liquid cooling is really only necessary when you are running a lot of extra hardware, or you're overclocking your equipment really hard for long periods of time, and you struggle to maintain low enough temperatures. That, or if your rig is too loud. Very few people really need water cooling. It's more a hobby than anything, at the moment. I might liquid cool my PC at some point, but the cost just isn't worth it for my uses in the short term. Also, they make noise dampening cases for those who need quieter builds.
Also, the 4690k can use Intel's boost to get it up to 3.9GHz, which is practically a 4.0 for your use. You really won't need to OC it to 4.0, because there will be practically no discernible difference to you. That saves you a little with power consumption, and cuts down on some heat. At a certain point, a faster processor doesn't necessarily give you better performance.