The Radiator
There is a HUGE range of radiators. Generally you will want to make sure you pick a rad with enough cooling power to cool what you have. A dual core SLI system needs at least a double rad and more likely a triple rad for better performance. If you have a slightly smaller system you can get away with less.
Good solid rads include: XSPC, Black Ice Xtreme and Hardware Labs PA120.
:wavey: HardwareLabs make Black Ice radiators. ThermoChill make the PA120 series.