Ok, so the list would be
PIV > AMD Athlon XP > AMD Duron > Celeron
PIV > AMD Athlon XP > AMD Duron > Celeron
Possibly... although in general AMD athlon will give you more bang for the buck than the Pentium's. The clock speed may be lower, but they have more efficient internals so they get more done in less clock cycles. Intel has some pretty high-end CPU's, but you will definitely pay a premium for it. Personally I don't see myself ever buying an intel again, they're yesterday's news.
(Especially the current dual core CPU's, AMD is spectacularly better than Intel. Faster, cheaper, and less hot)