Did you dig into the tests at Skinnees or Martins? Look into a few other forums for an hour or so?
I spent 3 months before buying my first WC part.
The amount of research you do is directly proportional to your amount of frustration.
Whats your ambient temps? Whats your fan noise requirements, are you going to pull room air through the rad or use hot case air to cool the rad? All of these factors matter.
You need to cool 250 watts under load. MAX. heavy load. Use Skinnee and MArtin to get the right rad.
Sr-1 series right here.
http://www.sidewindercomputers.com/hwlasrse.html
They are a link in the sticky.