For custom water cooling here are my thoughts:
Do you want a relatively cool and quiet computer? If so get a TR Noctua cooler and some good case fans.
Do you want a computer that is marginally cooler and costs a lot of money? Then go custom water cooling.
This might make you think I don't like custom water cooling, but it's the total opposite. If you want to take on a rather difficult project that ends with you owning a computer that looks incredible, is completely custom, and allows you to learn some new things then go with custom water cooling. It will sure as hell be more rewarding than just slapping a new cooler on your PC, and also grants you access to the Kingdom of Turbo-Nerdom.
Oh also use a secondary PSU when filling the loop, that way if it leaks you won't destroy your hardware.