I built a HTPC two years ago with the integrated Radeon HD 4200 and an AMD duel 2.8GHz processor and it plays HD. Based on the reviews I read it was pretty close to the minimum you could buy to play back blu-ray discs and other HD media without having issues.
I'm not 100% sure which Intel graphics chip you are talking about. I googled the Intel 4500HD and it leads me to believe it is the mobile equivalent of the GMA X4500, but I'm not really sure. If it is, then based on the Tomshardware graphical hierarchy charts it won't cut it since it is the mobile version of a graphics chip that is 4 tiers down.
However, I really thought the mobile i3's came with either GMA HD or HD Graphics 3000. The former might be capable, the latter would definitely be capable.