Basically it depend on how well u want it to cool off ur component as well as the noise level generated,,,

i m using Bigwater SE and Aquaris vga water block

my room temp is always hot during evening so have to use wc else things will get pretty hot....

anyway my result with the wc kit
idle load
CPU: 33 39
VGA: 53 60

Before WC
idle load
CPU: 43 55
VGA: 60 85

besides only 1 fan needed to cool off two conponents so kind of quite, if u got more budget go for dual fans radiator ...then it is really cool and quite

always remember problem of wc is the size of case, place to mount radiator, pump placement and the size of case to fit in tubings around

good luck dude