Apple is already running C2D on the MacBookPro (13 inch) and iMac (all but the top tier 27 inch).
They could find great replacements in AMD's line-up for a lot less. Nothing as good as an i7, and I've heard that TPD is a bit high, but AMD chips are fine if you don't want bleeding edge performance.
But that's the problem - most Apple consumers don't need bleeding edge performance, but the brand is known for having high quality components in their products. Perhaps AMD could find a socket in the Mac Mini, which is already positioned as a low-cost starter machine.
They could find great replacements in AMD's line-up for a lot less. Nothing as good as an i7, and I've heard that TPD is a bit high, but AMD chips are fine if you don't want bleeding edge performance.