I know it is only $150 difference but it's still money and I want to make a good decision which way to go. Info... I don't game on the Mac (maybe that's all you need to know). I mostly use for work which mainly has me reviewing PDF's of construction drawings. Also, utilizing VMWare Fusion for AutoCAD LT and some windows only programs I have. For fun I am probably a typical user with photoshop and some video editing. Nothing real heavy. My current setup MBP 17" with i5, 8gig, and NVIDIA GeForce GT 330M 512 MB is starting to bug me on the PDF side of things. If the drawing is large and complicated enough, navigating and zooming is not very smooth as the computer pauses to refresh the drawing often. Basically makes getting my work done take that much longer. Since the need to have a laptop as a main computer has changed and I would like to have two large monitors (I already have a 2nd 23" LCD) I want to migrate to a new iMac and pass along the laptop to another user. I have decided on all things except the GPU. Base system will be i5, Fusion, and 24gig memory. Based on my needs, specially related to my annoyance with PDF viewing, would the 680 serve me better than the 675 or does my use case make that choice irrelevant? Thanks for you input.