Doug has been taking a lot video classes with Adobe Premiere and After Effects, but his HP computer performance isn't all that great. Leo says that when you buy a computer at Costco you're not going to get a pro-grade device. If Doug is being slowed down by rendering, he'll not only want a lot of RAM, but he should also put in an SSD. A good NVidia or ATI Radeon video card will give him a fast GPU to handle the rendering instead of his PC's processor. That's what Premiere relies on -- the GPU.
Speaking of processors, an i7 wouldn't hurt either. It uses multi threading. Having more threads with a slower processor may not help him. He should go the other way with a faster processor and fewer cores. The GPU is really going to shoulder most of the load. Should he go with Apple? Leo says no. They don't keep up in the pro world. They've abandoned the professional market for the consumer market.
For video and 3D rendering, Leo went with Dell Precisions and top of the line dual GPUs. He can even go with a Xenon processor. It has more L2 cache, which is the single most important feature for video editing and performance of the processor. A workstation is going to be more expensive, but it'll give him the results he's looking for. Is Asus a good brand to buy motherboards? Leo uses the Asus Striker for his gaming machine and that's similar for performance.