Which case would be the best for water cooling? HAF X / Corsair 900d?

As I said earlier, its your choice, you could wait for HASWELL-E to come out, or you could go with Asus Rampage IV Extreme + 3930k(6 cores) or i7-4770K(4 cores) or Core i7-980 (6 cores) or Intel Core i7-3970X Extreme Edition(6 cores) or Intel Core i7-4960X Extreme Edition(6 cores) and over 1000$$

HAF X will handle WC properly and there is room for the radiator to fit inside the case(if that is what you are asking).

And enlighten me with an editing software which uses 64GB of RAM or even close !

I think its nothing to do with Comp Engg. but you got loads of money to smoke away, so you are trying to build an unbalanced PC.

I think you already know this but still if you have spare time read this :

A multi-core processor is a single computing component with two or more independent actual central processing units (called "cores"), which are the units that read and execute program instructions.[1] The instructions are ordinary CPU instructions such as add, move data, and branch, but the multiple cores can run multiple instructions at the same time, increasing overall speed for programs amenable to parallel computing.[2] Manufacturers typically integrate the cores onto a single integrated circuit die (known as a chip multiprocessor or CMP), or onto multiple dies in a single chip package.

Processors were originally developed with only one core. Multi-core processors were developed in the early 2000s by Intel, AMD and others. Multicore processors may have two cores (Dual core) (e.g. AMD Phenom II X2, Intel Core Duo), four cores (Quad core) (e.g. AMD Phenom II X4, Intel's quad-core processors, see i5, and i7 at Intel Core), 6-cores (e.g. AMD Phenom II X6, Intel Core i7 Extreme Edition 980X), 8-cores (e.g. Intel Xeon E7-2820, AMD FX-8350), 10-cores (e.g. Intel Xeon E7-2850) or more. A multi-core processor implements multiprocessing in a single physical package. Designers may couple cores in a multi-core device tightly or loosely. For example, cores may or may not share caches, and they may implement message passing or shared memory inter-core communication methods. Common network topologies to interconnect cores include bus, ring, two-dimensional mesh, and crossbar. Homogeneous multi-core systems include only identical cores, heterogeneous multi-core systems have cores that are not identical. Just as with single-processor systems, cores in multi-core systems may implement architectures such as superscalar, VLIW, vector processing, SIMD, or multithreading.

Multi-core processors are widely used across many application domains including general-purpose, embedded, network, digital signal processing (DSP), and graphics.

The improvement in performance gained by the use of a multi-core processor depends very much on the software algorithms used and their implementation. In particular, possible gains are limited by the fraction of the software that can be run in parallel simultaneously on multiple cores; this effect is described by Amdahl's law. In the best case, so-called embarrassingly parallel problems may realize speedup factors near the number of cores, or even more if the problem is split up enough to fit within each core's cache(s), avoiding use of much slower main system memory. Most applications, however, are not accelerated so much unless programmers invest a prohibitive amount of effort in re-factoring the whole problem.[3] The parallelization of software is a significant ongoing topic of research.

The terms multi-core and dual-core most commonly refer to some sort of central processing unit (CPU), but are sometimes also applied to digital signal processors (DSP) and system-on-a-chip (SoC). The terms are generally used only to refer to multi-core microprocessors that are manufactured on the same integrated circuit die; separate microprocessor dies in the same package are generally referred to by another name, such as multi-chip module. This article uses the terms "multi-core" and "dual-core" for CPUs manufactured on the same integrated circuit, unless otherwise noted.

In contrast to multi-core systems, the term multi-CPU refers to multiple physically separate processing-units (which often contain special circuitry to facilitate communication between each other).

The terms many-core and massively multi-core are sometimes used to describe multi-core architectures with an especially high number of cores (tens or hundreds).[4]

Some systems use many soft microprocessor cores placed on a single FPGA. Each "core" can be considered a "semiconductor intellectual property core" as well as a CPU core.