I am about to purchase my first Mac and I don't really know a great deal about computers, but... Is there a huge difference between the: Refurbished iMac 20-inch 2.0GHz Intel Core 2 Duo 20-inch glossy widescreen display 1GB memory 250GB hard drive 8x SuperDrive (DVD±R DL/DVD±RW/CD-RW) ATI Radeon HD 2400 XT with 128MB memory Built-in iSight Camera and the: * 2.4GHz Intel Core 2 Duo * 1GB memory * 250GB hard drive1 * 8x double-layer SuperDrive * ATI Radeon HD 2400 XT with 128MB memory Ships: Within 24 hours Free Shipping $1,199.00? Does the .4GHz make that big of a difference for a $250 savings? Also, how reliable are refurbished models? Are there usually cosmetic flaws? Thank you in advance!