I would vote for the 4670K and the GTX780.
For gaming, the 4670K will be stronger.
Actually, get the i5-4690K, the price will be similar and it has better thermals.
The i7 hyperthreads are not useful for gaming, and the stronger core speed potential of an i5 will overcome that when rendering.
For graphics, I like the GTX780 better. It might be a tad stronger than the R9-280X. It will take less power, cooling, and will be quieter.
How high you can oc haswell is determined by your luck of the bin.
Once you get past a safe 1.25v vcore, heat rises rapidly and no amount of cooling does you any good.
Better cooling may let you run at over 1.3 vcore, but that is no good for long term usage.
For that reason, I suggest a good tower type air cooler.
My canned rant on liquid cooling:
------------------------start of rant-------------------
You buy a liquid cooler to be able to extract an extra multiplier or two out of your OC.
How much do you really need?
I do not much like all in one liquid coolers when a good air cooler like a Noctua NH-D14 or phanteks can do the job just as well.
A liquid cooler will be expensive, noisy, less reliable, and will not cool any better
in a well ventilated case.
Liquid cooling is really air cooling, it just puts the heat exchange in a different place.
The orientation of the radiator will cause a problem.
If you orient it to take in cool air from the outside, you will cool the cpu better, but the hot air then circulates inside the case heating up the graphics card and motherboard.
If you orient it to exhaust(which I think is better) , then your cpu cooling will be less effective because it uses pre heated case air.
And... I have read too many tales of woe when a liquid cooler leaks.
google "H100 leak"
-----------------------end of rant--------------------------
I suggest a noctua nh-D15 or phanteks with dual 140mm fans.
Your pc will be quieter, more reliable, and will be cooled equally well