Radiator best place to set up.

Solution
For best cooling place the radiator in the rear fan position as an intake.
Make sure you have front and/or side intake for the video cards and hard drives.
And 2 or 3 fans in the top position as exhaust.

Most aftermarket GPU coolers dump most of their heat inside the case. Exhausting this hot air through the radiator will increase cpu temperatures. The above configuration will pull cooler room temperature air through the radiator instead of heated case air.

After installing a second video card my CPU temps increased 5c.
For best cooling place the radiator in the rear fan position as an intake.
Make sure you have front and/or side intake for the video cards and hard drives.
And 2 or 3 fans in the top position as exhaust.

Most aftermarket GPU coolers dump most of their heat inside the case. Exhausting this hot air through the radiator will increase cpu temperatures. The above configuration will pull cooler room temperature air through the radiator instead of heated case air.

After installing a second video card my CPU temps increased 5c.
 
Solution
Would you install a radiator on the bottom of the case or on top? Top mount I would do exhaust while bottom I would do Intake.

Hi,
Your best bet is to mount the radiator in the top with your fans mounted to exhaust air. This arrangement would remove heat from your system. Your other option was to mount the radiator at the bottom of the case with the fans mounted to intake. This is a bad idea. The result would put the heat that your are trying to remove right back into your system. Your NZXT 810 is set up to support a top mounted radiator, If you haven't added fans to all of your fan ports, now is the time. The front and bottom fans should be installed as intakes. The rear and top fans are installed as exhausts. If you have a side fan, of course it would be set to blow onto your video cards.