MacBook Should I get 2.0GHz or 2.4GHz? Is there a big difference? I sorta want the backlit keyboard... And I assume I shouldn't buy RAM from Apple? Time Machine Can I use any external hard drive for Time Machine, or do I need to use Apple's Time Capsule. Is it just me or is it overpriced? If so, why would I buy it? Do I need an external hard drive to use it, or can I back it up on my actual iMac? cheers.