Hey MightyMuch
🙂No on gets ripped apart for asking questions on ROG...
What is the Watts rating of your PSU. Those come with 700W right? Reference 780 wants 600W minimum so you should be just about OK. The EVGA SC cards are not exactly reference and come overclocked and would draw more power but it seems they have the same 600w minimum recommendation. You just wouldn't really have the room to OC anything CPU or GPU.
You would need a 6pin and 8pin PCIe power connector....I don't know if those PCs come with any spare connections on the PSU or modular cabling check that.
Finally the dimensions you will have to measure yourself...or wait to see if someone else has done the same mod and can confirm....