Dayummm

Asus has no mATX boards sadly  

Considering the 4690k and 4790k are same gen CPUs, and they have the same amount of cores, which is the more important factor than hyper threading. It wouldn't exactly "last longer". Though the 4790k does have a higher clock/turbo clock speed. But if you plan to overclock, you could hit around the same clock speeds with the 4690k. Again there won't be significant difference in gaming if you try to push cpu clock speeds.
 
Question you should ask is whether the additional 0.1 - 0.4Ghz you get from the 4790k, which might drive additional 1 - 5 fps is worth the $100. 
 
You could roughly save about $130, by getting a 4690k and a Hyper 212 evo. About $20 more and you could get a 980Ti. 
 
A 980Ti could easily push about 7-10 more fps than a 980.
 
Its just my two cent's worth.

Most games are not cpu intensive so overclocking a cpu might not do much, that being said, overclocking is somewhat a free boost in performance. So when you say "OC if possible eventually" what are the chances you will actually OC?

What's a gaming router? If he's playing via wired connection, it won't make much of a difference, it depends more on his internet plan's speed.
 
Maybe you could provide more details? How many people uses the net while he's gaming (if you know), his plan's speed, etc..

What's a gaming router? If he's playing via wired connection, it won't make much of a difference, it depends more on his internet plan's speed.
 
Maybe you could provide more details? How many people uses the net while he's gaming (if you know), his plan's speed, etc..