Well, I've written to some extent on this question about the HR-03-Plus and a fan.
My remarks about my motherboard ducting would qualify my remarks about fan choices, but I've discovered something about this particular cooler -- and possibly other VGA coolers.
In a "pull" orientation, I used a Panaflo 92mm that draws (I think) about 0.28A, and you can hardly hear it. At full bore, and aided with a 120mm exhaust-fan's "pull" through a motherboard duct connected to the 92mm's exhaust, it pulled down the GPU temperature with the HR-03-Plus to about 41 or 42C with room ambients of around 75F. More specifically, at idle the GPU temperature was 41 or 42C, and the load temperature associated with gaming that also loaded my Q6600 CPU to 50% usage was 42C. Under 3DMark06, the load GPU temperature climbed to about 47C, and that represents a 5C-degree spread.
But I get approximately the same result -- again with the ducting, and this time with a "pusher" fan that's an 80x15mm Zalman OP-1. At it's top end of 3,125 rpm, you still hardly hear it at all.
How this relates to a situation without the ducting and a comparison between the 92x25mm and the 80x15mm fan or a 100 or even a 120mm fan depends on what is the minimum temperature for an 8800 GTX (or an 8800 GTS) with HR-03-Plus when the cooler has reached its minimum thermal resistance. I suspect that a minimal thermal-resistance situation for the HR-03-Plus brings both idle and load temperatures within 2 to 7C of 40C at "normal" room ambients of (say) 70 to 75F.
The 15mm fan-thickness for the Zalman fan resolves at least partly a problem of the cooler precluding use of some PCI or PCI-E slot, and it also may resolve a problem in the second "installation option" for the cooler where the fin-and-fan assembly interfere with the CPU cooler. I think I recall seeing a Panaflo 80x15mm fan as well, that had similar specs to the Zalman, and you could get one of either for around $6. Also, you could probably fit two of them on an HR-03-Plus, and that wouldn't appreciably increase noise-level: you might actually be able to run them both at lower speeds and get more overall CFM airflow at significantly lower noise levels.