While it's not that exact product, I have an HD 6970 with an Accelero Hybrid cooler on it (same basic idea) and it does do a good job cooling the card. Probably 15 - 20 degrees C better than the stock cooler. I used to have an Accelero Xtreme cooler on the same card (air cooling only) and the hybrid is a few degrees better than that was at its best (as it aged, the cooling power diminished, possibly the heat pipes leaked?).
In the same system, I also have a Corsair H70 on the CPU. The one thing you need to be aware of is it can be difficult to route everything around in the system with 2 closed loop systems. I don't know what the reach on the NZXT is like, but the Accelero Hybrid had to go to the rear or bottom of the case (HAF 932) - for my setup, it worked best mounting the fan & radiator on the bottom intake next to/behind the power supply with the fan in intake orientation.

-Dave

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