My plan is to replace my iBook shortly with a refurbished MacBook. I'd like to get a model as inexpensively as possible and upgrade the RAM and maybe hard drive myself. My question is: which processor to go for? This morning, there was a 1.83 GHz Core Duo for $800, a 1.83 GHz Core 2 Duo for $850 and a 2.0 GHz Core Duo also for $850. Is there much difference between these models or am I just splitting hairs?