Wanting to buy a custom loop

[Reality|Bites]

So I've recently bought a 7700k clocked to 5Ghz cooled using a Corsair H100 RGB AIO but
the temps hit the low 70's while gaming in cool weather and I have to down clock to 4.8Ghz at the moment while it this hot.
How much better would a custom loop perform and is it even worth it?

Which bits of kit would you all recommend? should I be buying a bundled kit or individual parts?
I'm confused by the tubing and fitting sizes as well.

 

[Reality|Bites]

Yeah I have a delidded one too. on the box it came in it said only a 7C improvement from stock, I think I was given one of the runts really.

 

[Reality|Bites]

I'm using 1.31v for 4.8Ghz (still to try lower) and 1.365v for 5Ghz.