A:AnswerThe motherboard doesn't support RAM speeds above 2666 MHz. The included RAM is HyperX, but I'm not seeing any reference to it being HyperX Fury.
A:AnswerYes you can install an internal hard drive. I don't know about cables. Here is the link to the upgrading and service guide:
http://h10032.www1.hp.com/ctg/Manual/c06140594