At its default clock/voltage settings, Intel's Core i5-750 uses a lot less power at both idle and under load than the Phenom IIs, despite the fact that both processor families are etched at 45 nm.
The Core i7-920 is an early Bloomfield sample with a more complex memory controller and a complementary platform based on two chipset components, rather than one. As a result, system power consumption on the -900-series chips is almost always going to look higher than the Lynnfield- and Clarkdale-based parts.
The overclocked Phenom II X6 1100T blows the roof off of maximum power usage when overclocked, though. This is a surprisingly high result, and we ran the test multiple times to ensure its validity. It's a good thing that, the same chip at its stock settings, is much more power-friendly.