Hi I just bought a 144hz external monitor (ASUS VG248QE) for my iMac. The reason for the 144hz monitor purchase is gaming, and as I still love my iMac, I have no plans to buy a new PC desktop computer, so I simply bought a Mini DisplayPort to HDMI cable between them. According to the person at our local Apple retailer this would be no problem at all, and this would work fine. It did work in a way, the screen is running and there was no problem as far as that goes, except I can't set the screen to 120/144hz, the highest I can do is still 60hz. Why is the local Apple retailer telling me a Mini DisplayPort to HDMI cable works, when it seems like it doesn't? Or does it? And I'm just missing something? Please help.