Is that 64*C in games? My card is loaded 99% when I am showing my temperatures. In games it shovers at 62-64*C only but distributed computing such as MilkyWay@Home or bitcoin mining is what I use it for. So the gaming temperatures are not accurate enough for my purposes. But yes, the Sapphire DX cooler is very very impressive.
I thought you got the dual-fan HIS IceQ X². The $600 "X" card and your HIS IceQ X² card have identical coolers. Vanilla means reference blower design with 1 loud fan. :\
The card that's on sale for $395 is the
HIS IceQ X² with a huuuuuuuuuuge cooling heatsink. It's going to be > 12 inches long from the looks of it.
Great advice from you on overclocking but the bolded part, caution! HD7970 unlocked is
1665mhz. You don't want to do that on a 7970!
The sweet spot for a HD7970 is usually 1150-1175mhz on stock VDDC voltage of 1.175V. After that, it's usually 1200mhz on 1.20-1.225V, 1230-1250mhz on 1.25V, 1250-1280mhz on 1.30V. Of course not all chips can do the latter increments so what may happen is some chips won't go above 1150-1175mhz even at 1.30V, that's when you lower the voltage to the least possible value, and maybe back off the overclock another 10-15mhz to stay on the safe side.