Go with the Athlon, or if your really strapped for cash the Duron (supposedly it's rated on average 90% of the Athlon). Right now the only two probs with AMD chips are heat, just get a good hsf at least a Cooler Master, and gaming issue under Win2K but AMD has a patch on there site. Either go with the Asus A7V or the Abit KT7 they're the only ones you want if you're going for performance. If you want to OC an Intel you have to do it by the FSB, while AMD's chips have to have the L1 bridges closed. Just use a #2 pencil to do this.
Unless you want to have a dual proc system or don't want to worry about the CPU getting hot, don't go with Intel right now. Nothing wrong with Intel, but performance isnt coming from them.