Any of the choices here seem like overkill to me for what you want to do. I'd personally sacrifice a bit of encoding speed for a laptop with much less weight. Laptops with the ultra low voltage PIII chips can hit up to 7 hours of battery life, usually can still play DVDs and such on the go, offer a much smaller form factor when lugging it around, and allow for better "laptops" when sitting somewhere on a wireless network.