I disagree with whoever said that AMD has lost the performance crown. Yes the core duo goes faster than a lot of AMD stuff, however the core duo isnt a bang-for-the-buck processor. Its a look-at-me-ive-got-money-to-blow-on-whatever-i-want processor.
If you want to build a budget machine, there are many routes you can take. For example, for a gaming machine, you dont need the best of the best of the best. Some of the best budget gaming machines out there are Celeron D's for christ sake. The Sempron platform is fine for gaming also. Also, believe it or not, you can buy a Pentium M motherboard and proccy for cheap, overclock the summabitch out of it, and that makes a great desktop machine too because Pentium M's were built for low heat and power consumption in laptop situations.
However if you do a shit ton of video stuff, like encoding, transcoding, and the inbetween, that is a situation where you need the best of the best, or just a step below it. A step below it would be, like in an above post, an AMD X2. Just look for sweet deals on the internet, sometimes you come across stuff that you will find to be too cheap to pass up.
If you just do web browsing, go to a cheap computer store and pick up a PII-266 for $20.
/2 cents