Neospiral's question is really important. If OCing then you need really good cooling.
I am using, have been for a couple years now, a Corsair H50 with dual fans. I do NOT OC and I have been really happy with the temps on my 8120 cpu. Corsair has an excellent reputation and the install is easy and there is no real maintenance.
If you plan to OC, and still want the convenience of pre-built liquid cooling, then consider the H80/H80i or even the H110/110i if your case has the room.
Of concern with ANY liquid cooling is leakage: Usually when they leak they destroy equipment (your PC). Some web searches of USER reviews of the Corsair systems and other types and brands of liquid cooling will help with your decision; from what I have read the leaks on the prebuilt systems often stem from people bending the hoses/tubing a lot or trying to remove them or shorten them.
Neospiral, jump back in here please.