Hi! I have a new iMac 3.06ghz with a ati 4850 graphics. I want a mba for something portable. i am getting it from ebay because they are much cheaper and you can get the live.com discount. That being said, is there a noticeable difference in the 1.6 and 1.86ghz processors? Also, can you upgrade the hard drive to an ssd yourself? Thanks!