Both the cases mentioned are beasts, with fantastic air-flow and are very large. Larger than I might recommend myself. I believe one has 3 fans and the other 4 fans. Either offers more expandibility than you could ever use.
I don't know anything about water cooling, but unless you plan to learn and do a lot more with extreme Overclocking, I woudn't worry about it. These cases provide top-of-the-line cooling combined with the good CPU coolers. Plenty for any typical OC. And likely would be fine with water coolers too.
The Intel i5 is a lower-end alternative to the i7 family. All i7's are quad-core, as are some i5's, but the i5's also include some dual-core models. Regardless, both lines are fast and capable. Generally, you can compare the GHz of a type of CPU within a family as the higher the MHz, the faster the processing speed. Once you change the # of cores or the family, you can't really compare. That is, using imaginary models... an i5 2-core at 2.8GHz will be faster than an i5 2-core at 2.6GHz. But you compare a i5 4-core @ 2.8GHz to an i7 4-core @ 2.6GHz, the faster cpu isn't so clear. I am not an Intel CPU user or expert.