Listen to this guy...this has got to be one of the smartest responses I've seen in this thread (and I read the whole thing).
The AMD combo
stock clocks, will perform roughly on par with the Intel combo
. However the Intel will fall behind in the graphics department (stock clocks of course), and the AMD will fall slightly behind in the processor department. If you ad a new graphics card, the AMD will still pull ahead...and even further thanks to hybrid crossfire.
However if overclocking, AND you add a discrete dedicated graphics card, then the Intel will win. It just depends on what you're doing. If you plan on staying stock clocks, I'd recommend the AMD with 780g chipset. You CANNOT go wrong with that for a media center use. That's what most of the smart people around here will use in their HTPC rigs (media centers).
If you plan on doing heavy CPU tasks, and some light gaming, I'd recommend the Intel combo with a dedicated graphics card.
Its really up to you. Either one will be a good deal faster than your current Pentium 4. And will BOTH be very comparable at stock speeds. It just all matters on what you'll do with it if you overclock, or plan on gaming with it.