Originally Posted by nleksan
The QP is a low-FPI thin rad so it's optimized for low speed fans and, in all honesty, doesn't have a whole lot of thermal dissipation ability. I would say it's probably equivalent to the UT60 2x120. I really do hate to be the bearer of bad news, but in my opinion you would be far better off returning the QP and ordering either the XSPC EX or Alphacool NeXXos UT60, as with the qp you will need another rad to cope with both which raises the cost above what a single 3x120/140 rad from either of the aforementioned companies would cost :/
The QP stands for "quiet performance" and while thick rads with 8-11fpi are typically good performers, when you cut the depth in half without changing anything, you sacrifice a lot of performance.
Just to let you know, the EX420 can be had for $69.95 @ Jab Tech, the EX360 is $7 less, and the Alphacool NeXXos UT60 is about $20 more than the EX per size.
With a 420 rad, you will have to drill 8 new fan screw holes, but it is simple if you have a drill, just remember to measure twice and drill once. I am a proponent of the 420mm radiator up top as it gives you slightly more surface area than an equivalent 480mm radiator. Basically, you would get a DeltaT of around 13-16C with the QP or 6-7C with either of the other radiators. That is a huge difference, and as you are just starting out, laying down a strong foundation will save you a lot of money and time down the road.