Oh thats cool! Does the case have enough room in the back for an adapter? I chose the Asus motherboard because it has 2 m.2 ports. One on the front and one on the back. I was thinking about routing it from the front and bringing it down. But if theres room in the backside then that opens up motherboard options for me.
There should be plenty of room, since the cable is just a ribbon type. I think routing from the bottom may be the only option, since an occupied PCIe slot would block the ribbon on the top. I would send an email to ADT-Link and see what they say. It looks like the Elgato HD Pro is PCIe x1 and may not require much power. I would also ask Elgato what the max power draw is. I imagine you've already looked at the HD60 or HD60 S? Being external they would obviously be the easiest option.