LucShep

You've left important pieces of information that will make it easier to help you decide (and save money).
Now, let's see in parts... :-)
 
.The i5-4690K is worthy only if overclocking. For that, you would want a Z97 motherboard (same for Z87, but it's previous gen.).
But, in your case, as you don't want to overclock, the extra expense on both "K" processor and Z97 mobo would be wasted.
 
The best thing to do in your case is to get an i5 4690, an H97 motherboard, and good ddr3 1600 RAM (8GB or 16GB, depending on your budget).
 
In regards to H97 motherboards, here's some that have been well regarded:
 
- AsRock H97 Performance
- Asus H97-Plus
- Asus H97-PRO
- Gigabyte H97-D3H
- Gigabyte H97-Gaming 3
- MSI H97-Gaming3
 
All of these are good, some have things and features that others may miss (intel Lan on some, realtek Lan on others, more and less usb ports, etc).
I would recommend looking at the specs of each, look for some reviews in the internet, etc, then choose accordingly.
 
.Both the Nvidia GTX760 and the AMD R9-280X are both good GPUs to use for 1080P gaming.
 
The Nvidia GTX760 (any model, OC or not) has the upper hand in wider compability due to Nvidia drivers being generally better (hence better performance in some games).
It also consumes much less power, which also means that it'll run cooler when stressed.
 
On the other hand, the AMD R9-280 is an excelent GPU, it has a bit more "umph", and also more VRAM (50% more), which is becoming important. The problems it could have for you is what was mentioned - AMD drivers are problematic with some games (although perhaps not with the games you plan), and it does use more power (gets hotter).
 
With that said, I would strongly consider the GTX970 (any model, even a vanilla model from Nvidia will be good).
With that beasty i5 4690 processor, believe me, it's a phenomenal combination that you'll appreciate in the longer term. :)
 
 
.The i5 4690 processor is beyond any question or doubt. It'll even game at 4K if you throw a top GPU for it.
Pair it with something like 16GB of memory and I'm convinced you got enough processor and RAM mem for the next 5 years of gaming.
 
You'll be fine with either GTX960 or R9 280X for gaming at 1080P, no doubt. The real question is for "how long" (...and "what if other new or more intensive games suddenly appeal"...).
 
My take on a PC investment is that sometimes budgeting and cutting corners doesn't pay up later - especially on the relevant things (I learned the hard-way... don't be like me! *sigh* lol).
You don't want to spend the next years cutting settings down to keep framerates, nor hiting a wall in VRAM in a a festival of hi-res textures.
Again, if you manage to afford the GTX970, do it. It's noticeably faster and has more VRAM than both those two, it'll keep you more satisfied for a longer time.
 
If you ever need help chosing the RAM, the PC-case, fans, storage, PSU, bring up the questions.