I been looking at a refurbished 2.53 GHz 15" Macbook Pro (4GB DDR3 ram, 512MB 9600GT, 320GB hard drive) for $1449 from Apple's website. My sister contacted me saying she is able to get a 2.4 GHz 15" Macbook Pro (2GB DDR3, 250GB hard drive, 256MB 9600GT, and 3year AppleCare) for significantly less than that. What are the limitations of the 2.4 GHz model? Are there any major differences between the two CPUs other than the clock speed? What is the max ram the 2.4GHz MBP can address? Will there be significant differences between the two?