Oh, you asked us a similar question around two weeks ago. The answer is still the same. Your power supply will be fine for now as long as you're not overclocking.
I think you're talking about this Powercolor R9 390, it measures 305mm long so it's a bit too large for that case.
What are you doing on your PC that you want to get an i7 6700K? You could get the i7 4790K (as low as $300) for cheaper and it would perform fairly similarly to the i7 6700K. You would be able to reuse your existing RAM and motherboard with it as well.
An even cheaper solution would be the Xeon E3 1231v3 ($245 at the lowest). It's similar to an i7 processor it that it's also a quad core model with hyperthreading, but it does have a lower clock speed of 3.4GHz to 3.8GHz.
Yea I'm going to buy this Friday and was considering the gtx 970 at first then went to to a 390. I guess will have to go back a 970...if it will fit in the case.