Well, I would still go for Athlon64 3500+, it being in the perfect price/performance slot. Check the Anand's newest single-core performance measurements:
http://www.anandtech.com/cpuchipsets...oc.aspx?i=2429
What seems to my eye there that AMD is leading quite nicely where it matters. I tend to ignore the synthetic benchmarks because it's been proven many times that they have little or no relevance to real life.
So on those non-synthetic benchmarks that P4 leads, it has at most 1-3% speed advantage on similary priced Athlon. On those that Athlon leads, it has usually 5-15%+ lead. Go AMD.
Also, if you want to go dualcore later on AMD, you just update the BIOS. With intel, it's a MB change for you. Also, if you check the new Intel roadmaps, there's another huge phaseout before the next-gen processors come out (meron & co.).
AMD is a no-brainer if you want performance and more security on your already poor investment
