There is no real decision here: The Xigmatek is $18 after rebate at the egg. http://www.newegg.com/Product/Product.aspx?Item=N82E16835233003
I have direct experience here. On a whim, I saw the sale at the Egg, and bought the Xigmatek to replace my AC Freezer 7 Pro. I was a big AXF7P devotee, but the X dropped my temps by nearly 10 degrees.
At 1.36 volts and 3.85 MHz, my e8400 C0 idles at about 36 degrees (thats the hotter core, but the cooler-and-presumably-broken core idles at 31 degrees) and barely cracks 50 degrees at full 100% Memtest + Prime95 load. For the same situations, with the ACF7P it idled at about 40 and hit into the low 60s, reaching 63 or so.
The X is also a notch above the AC in build quality as well. I briefly researched the X before buying it, and there were a few reviews that placed it as either the #1 or #2 best available cooler. http://www.frostytech.com/top5heatsinks.cfmhttp://www.tomshardware.com/reviews/cpu-cooler-charts,1967-12.html
The only negative comments were about its push pin connectors. But these connectors are the identical ones as on the AC (probably same OEM firm made them). If you take 30 seconds to sketch the lock vs. unlock configuration on a piece of paper, you will get it mounted on the first try in under a minute.