The Radeon 290x > nVidia 780. The 780ti is another story though. However, since the cheapest 780ti I see is 640 dollars, and the cheapest 290x that I'd buy is 495, that makes it easy to choose between them.
At similar price points though, it would depend on games to decide between the 780ti and 290x. For reference, right now:
Some people will say Nvidia features are, others won't. Personally, I say meh. Amd has mantle and what not as well. I'd go with the r9 290x over Gtx 780 without question.
But my power supply is good enough and im willing to pay, also are the nvidia features worth it?
Your PSU is easily enough! Go AMD, they are offering quite a punch with their R9 290/X series GPU's.
Will i need to custom cool, the temperatures listed on some sites show that it is almost possible to make breakfast an the thing! And also i heard that CF's drives are BS.