It's true as they say, dual core will inevitably be faster for multitasking, though not as stable sometimes, from my experience. It really depends on whether you want to save more on the battery (Celeron), or multitask and sip a bit more power. Believe it or not, I was once tried using a Celeron to run Adobe After Effects CS3 - and it managed. Another choice you have here is between two reliable brands. Toshiba, being the more efficient and reliable of the two can balance out this match depending on the way you like to use your comp, focused, or multitasking.
I also recommend Tiger Direct if you want the most bang for the buck. Good luck!