I guess I'll be somewhat repeating what Finn said, but it's essential to understand it.

Having a balanced PC build is essential if you want to get the most out of your system. While aesthetics might be important to you, you should consider the practical importance of the system to you. You probably won't spend hours and hours looking at your computer, but you will most definitely spend thousands of hours using it. That is why you should try to get a good balance between your components.

As Finn already mentioned, liquid cooling is not necessary in your case, but hell, if you want to have it then sure it doesn't hurt anyone.

SSD, HDD and PSU are very cheap considering that you got 1080 and i7 8700. I would advise against cheaping out on certain components just because "they don't bring processing power". With a bad HDD or SSD (which I'm not saying that yours is bad, just worse than average) you are going to have lag on your games despite having 1080. With cheap PSU you are putting your system at great risk, which could even cause damage to your components in the long run.

If your budget is tight I'd rather downgrade the GPU and get more balanced components.