On the zd7000 series, it will only cost you $100 to go from a 2.66p4m to a 3.06ghz, but another $200 on top to go to 3.2ghz. So the 3.06 is a great value, at least on the zd7000.
On the other hand, upgrading the 8500 dell to a 2.6 from a 2.2 will cost you $300, go figure.
the zd7000 is by far...