All your hardware for building the computer system is cool except,(my opinion) you should go with Nvidia's graphics card with at least 256mb. 128mb ATI card is cool, except that you mentioned you do alot of video encoding as well as hooking it up to a entertainment system. As for Ram, I agree with some of the other comments on here, 2x512 PC3200 should be the minimum for you since you have 800megahertz FSB. This should take advantage of it.