i7s are actually starting to show their usefulness in gaming, games such as battlefield 1 take full advantage of the 8 threads and PC exclusives such as Star citizen are recommending an i7 for the optimal experience. with that said you can't go wrong with an i7 specially on a 1500+ budget.

Watercooling can have it's advantages of giving your system a good look but is a bit pricier than air cooling if you're going with a high end AIO like the corsair ones. since your CPU is locked and your motherboard is a H170 chipset, my guess is that you're not looking to overclock, an air cooler such as the Hyper 212 Evo is totally fine.

For monitors that 24 inch 1080p AOC is more than enough for your needs, specially that its a replacement for a TV. you'll see a major improvement with it.

Lastly, i don't know if that case is your personal choice or budget oriented, but it's extremely expensive for the looks at least. the NZXT S340 is one of the best looking cases out there only for €70. but it's up to you.

Here is a fix list with everything above included.
PCPartPicker part list / Price breakdown by merchant