Also, if we're talking high end processors, we aren't talking about this particular device
A 2.8GHz single core is a pretty careful choice. It's a pretty good balance that supports a wide range of content, remember not everything supports multiple cores well (or hardware acceleration for example). This processor does everything up to 1080p24 (what you see on apple.com for example) and also supports flash video, etc. On one hand, there's a great deal of discussion of ION or other graphics centric solutions, which are great when that hardware matches *exactly* what you want to playback, but then try something not optimized (flash for example) and you are very limited. On the other side, there are more powerful CPUs, but the expense (and cooling requirements-noise go up) and in most applications you won't see one lick of improvement, I know because we tested a lot of them before settling on this one.
"Your mother was a hamster, and your father smelt of elderberrys!" -- Monty Python and the Holy Grail