i think
Athlon 64 > P4 > Athlon XP > celeron
and
ATI > NVidia
Athlon 64 3400 and FX outperforms P4 extreme, and 3400 is half the price, but the FX is still too much $; I used to like P4's better before they made Athlon 64's
but I would definately go with P4 over Celeron