For a pc with a 280x, you need at least 600W
The 4690 doesn't overclock. Its about $20 cheaper than the 4690k. The 4690k though has higher clock speeds than the 4690 even without overclocking and so would still perform better. So get the 4690 if you definitely never want to overclock. If you get the 4690 you also won't need an overclocking motherboard (Z97). You van then also get one of the cheaper H97 motherboards. But they can only fit one graphics card. If you possibly want to fit a second graphics card down the track then get the Z97.