x86 is the cheapest for the money. What would be cool is if someone did a radical type of motherboard redisign and included multiple gpus, incredible sound card components and and multiple upgrade slots for adding MANY x86 processors, maybe additional coprocessing components and so on.
16 core chips will soon be very common... Imagine 4 phyical 16 core chips on one motherboard, or more, with great gpu, sound, ect, all on one slick mb that you can upgrade for many years.
Steven