Definatly AMD if your on a budget. No question.
Also check around OC forums classifieds section as well (must be a member and have a certain number of posts I think, not sure as I passed that number of posts quite some time ago ) but there's often good things in there goin cheap, and the guys are pretty reliable too.
But definatly AMD for a budget computer. Or even if on a severe budget get a Duron
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