This link shows some differences and that they can play HD but, it depends on your CPU model. http://www.techpowerup.com/reviews/Intel/Core_i5_2500K_GPU/
The chipset you have plays video at 24fps - the issue is video actually plays at 23.976 fps ... so what happens to a display that refreshes itself 24.000 times per second? You get a repeated frame approximately every 40 seconds to synchronize the source frame rate with the display frame rate. That repeated frame appears to your eyes as judder in motion, particularly evident in scenes involving a panning camera. How big of an issue this is depends on the user. Some can just ignore the judder, others will attempt to smooth it out by setting their display to 60Hz, while others will be driven absolutely insane by it.
Now, to address your actual question, it seems you use the PC like me - I don't do games, but I do web / Photoshop / In Design (and even basic movie edits). I don't use a GPU - the built-in is fine.
However, I also don't care if my DVD plays in HD or not! As long as it's not pix-elated I'm happy, but this will be the only point of concern for you (if you need HD or not).
The only other thing which a GPU would allow is multiple monitors - for example, I brought a GPU simply because I wanted 3 monitors.