Well clock speed as in the Ghz number isn't as big of a factor today as it once was.
This is taken from the sticky at the top of these forums:
"THE SHORT STORY
The frequency of a processor is almost irrelevant. The only thing that determines its performance is how efficient it is with its clock cycles. The Athlon 64 is more efficient than the Pentium 4 so can out perform it at a lower clock speed and the Core 2 Duo is more efficient than the Athlon 64 and can out perform it at a lower clock speed.
Core 2>Athlon 64=Core>Pentium 4"
That's the short saying for it. Nitestick wrote it and did a good job. If you want to read the rest, click this: