Looks good so far, but I'd just go with the 3.0C. The 3.0E Prescott runs hotter, and has no real performance gains. If you're buying a Socket 478 motherboard and using air cooling, going with a Northwood (3.0C) seems like the way to go.
Also, I don't want to send your hopes to the skies incase you end up with a dud, but you can expect well over 3.3 from a 3.0C with the stock Intel HSF. It took me a matter of hours tinkering to push my 3.0C past 3.6, rock solid stable, with no TIM and the stock HSF.
One thing I would consider if you're planning on overclocking is faster RAM. Buying PC3200 is the only thing I regret about my most recent build. Good RAM like you're looking at should have no problem being pushed, but buying PC3500 or better can only help.
Also, I'm not so sure about that Aspire PSU. I think most people on here would urge to to consider a Fortron or Antec PSU.
The only other thing to consider you might have overlooked is utilizing the RAID capabilities of your motherboard with a couple of Western Digital Raptors. If it's in the budget, I think most people on here would consider it a worthwhile upgrade. I love mine.