From server demos, 2.5Ghz Shanghai has same idle power with either 1.8Ghz or 1.9Ghz Opterons.
It wouldn't be far to say that the Phenom Is are the same as 65nm Opterons.


From here http://www.madboxpc.com/review-amd-p...0e-x4-9150e/6/
We see that the EE 65W Phenoms take the same power in idle as they're in the same voltage bin. Same applies for tri-cores, we see a trend here.

And then there's this: http://images.anandtech.com/graphs/a...5125/17176.png (I hope Shintai's looking, as it's his fave site)
There are 2 P-II X3s, 2.8Ghz and 2.6Ghz. Both probably are in the same voltage bin in terms of idle.

So if an 2.6/2.8Ghz X3 uses same power as E8400 at Idle, it's quite nice. At load it will use more though, can't ever avoid that as it's 3 vs 2.