Yay, first post on this section ! 
I read the manual and it said that it was GPU powered so if I upgrade my graphics card to a 480gtx will I see an improvement in the viewport ? I have a 8800gts at the moment.
yes, it is GPU powered, however there is no guarantee that the newer and faster cards will give better results. the GPU preview is writen in DirectX 3.0 shader language and perhaps the translation (that is made by the driver) to the native card language can be more or less efficient. i have seen real examples, when an old card runs the GPU preview times faster than new and expensive card.