I'm trying to find out what my old fan's lowest speed was, but no luck. The only thing I can find by looking for its model number (PLB06625B12HH EP) is that it's 2 ball bearing with a max rpm of 5000. Nothing about lowest, however seeing as the original bios let me drop the speed to 22%, I'd say it's around 1100 rpm and I do remember it being a lot quieter at idle, I'm just not sure whether it's a straight swap.
Old HG10's relied on you replacing the fan with the stock blower fan, but with this line, the compatibility was expanded to all reference board cards, not just reference cooler ones, so Corsair started shipping their own fan with the bracket, but they never said if the fan is the same is the same as the reference one. The dimensions stated are roughly the same (70x25 vs 66x25) and it's the same type of fan with same type of mounting, but I've no idea whether the mounting holes are a match without taking it apart first.
Dustin?