I want to buy a new iMac but cannot decide between the iMac 17" 2.0 (EDU $1100) or the iMac 20" 2.16 ($1400). Are worth the $300 for the extra 3", .16Mhz, and 90GB of hard drive? If I pick the 17" I would buy an external hard drive. I cannot BTO de hard drive because im going to travel and I would receive the Mac after leaving. Thanks.