Planning on getting an iMac and building a gaming computer. Was thinking I could save some money by using the iMac as an external monitor. It's got a great picture no doubt but what would be the response time and refresh rate if I were using it as such for a PC? Also, what ports would I use to connect it? HDMI? USB 3.0? Thunderbolt? (Yes, I found a PC motherboard with Thunderbolt).