General Hardware Recommendations

The more cores, cache and the higher the clock speed, the better. Intel processors are preferred over AMD, that lack full SSE 4.2+ support and have a very slow SSE 4.1 implementation, which is heavily used during CPU intensive (read AVCHD, MPEG taks). The basic entry point level for new systems appears to be the i7-2500K/2600K for economical systems and the i7-3930K/ 3960X for more high-end systems. i7 systems from any series below the 25xx series are not advised, let alone the i3 or i5 series. They suffer too much from the memory controller, the chipset on the motherboard or the lack of Hyper Threading.

The more capabilities to adjust clock speed and memory speed, the better. Overclocking can lead to substantial gains and HP / Dell and the like do not allow that. Be warned. The major brands suffer from lack of overclock ability, fixed (low) memory speed and configurations unsuitable for editing. Better build yourself or turn to a reputable custom builder with demonstrated expertise in video editing. X79 motherboards are currently the best choice.

Definitely use a CUDA/MPE capable video card. It can reduce rendering time by a factor 10 or more and assists with scaling on export, while improving export quality. SLI is no consideration, since it is not supported. For the time being ATI is out of the game and only nVidia cards with 1 GB+ video memory are worth considering.

Specifically for MPEG encoding, the amount of memory is critical. The more the better. 24 GB is far better than 12 GB. The faster the memory, the better. First is rating (1600 or 1866), then CAS latency. Use at least 12 GB but preferably even more. To use the faster memory, BIOS adjustments are required.

The faster the disk(s), the better. Raids do improve performance. Notice that all Top 20 Performers use Raid configurations and sometimes even multiple Raids. Even SSD's, though widely touted for their speed, benefit significantly from Raid configurations.