2 things:
#1. This whole concept of building for $650, $1250, and $2500 should be about the best bang for the buck, but geared towards who you're building it for, not Intel vs AMD. Gamer, Workstation/Gaming on the side, Graphic Designer/Video Editor, etc.
#2. This whole Builder Marathon seems more to be about a gaming machine if you had to spend $650, $1250, and $2500 now. For all the articles Tom's Hardware has, why does any gamer need anything more powerful than a Phenom II x3 720 BE? Why does any gamer need anything more than 4GB DDR2 RAM? Is the extra 5 FPS actually worth $300? These are the things I'd like to see. You then realize, hey, instead of building a $1250 system now, I can build a $650 system, and upgrade in another 6 months because the value is better than the gains.