You can add a SSD for the OS drive and that would make the overall perfomance of the Pc a little snappier and programs would open faster and web pages too.
What specificaly do you want to speed up , productivity or gaming? What OS do you have?http://www.tomshardware.com/reviews/gaming-graphics-card-review,3107-7.html
This is a chart of all the video cards and where they fall in order from top to bottom and which cards from each comany compares to the other. It looks like a 6870 or a 560Ti would be an upgrade for the video card. How much are you looking to spend on this upgrade.